Cu- and Ni-Catalyzed Decarboxylative Borylation Reactions

ABSTRACT

The invention is directed to methods of converting a carboxylic acid group in a compound, via a redox active ester, to a corresponding boronic ester by treatment with bis(pinacolato)diboron-alkyllithium complex in the presence of a ligand, a Ni(11) salt or a copper salt, and an Mg(11) salt, in the presence of an alkyllithium or a lithium hydroxide or alkoxide salt. The product pinacolato boronate ester can be cleaved to provide a boronic acid. The invention is also directed to methods of preparing various compounds of medical value comprising boronic acid groups, and to novel boronic-acid containing compounds of medicinal value, including an atorvastatin boronic acid analog, a vancomycin aglycone boronic acid analog, and boronic acid containing elastase inhibitors mCBK319, mCBK320, mCBK323, and RPX-7009.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under GM-118176 awardedby the National Institutes of Health. The government has certain rightsin the invention.

BACKGROUND

Boronic acids are of paramount importance to all facets of chemicalsciences.

Although their popularization and widespread utilizations can likely beattributed to the incredible utility of the Suzuki coupling, (1) todate, boronic acids have found countless applications in fields faroutside of cross-coupling, such as materials science, (2) chemosensors,(3) polymer science, (2) and drug discovery. (4-5) In medicine, twoalkyl boronic acids are currently approved by FDA for various oncologyindications: ninlaro (1) and velcade (49). Medicinal chemists point tothe bioisoteric nature of boronic acids as they can function in certaincases as a carboxylic acid surrogate. (6) Despite their popularity,boronic acids are almost entirely derived through synthesis unlike thecarboxylic acids they seek to replace which are ubiquitous andinexpensive. The retrosynthetic analysis employed in such cases canitself be a deterrent to their incorporation into a drug candidate.

As illustrated with 1 (FIG. 1A), the conventional approach focuses allstrategic attention on the means with which the boron atom will beincorporated even though this represents <5% of the total molecularweight of 1. (7) The synthesis of an engineered amino acid (AA) istherefore required and each analog must be made individually. Incontrast, the direct transformation of the carboxylic acid containingnative peptide to the corresponding boronic acid at a late-stage wouldbe far easier and more logical from a strategic perspective. Given thesheer number of alkyl carboxylic acids in feedstock chemicals, naturalproducts, and drug molecules, this transformation could provide theunique opportunity to expediently procure a myriad of previouslydifficult-to-access boronic acids as versatile building blocks,functional materials, and potent medications.

SUMMARY

This invention provides, in various embodiments, methods for theconversion of a carboxylic acid group to a boronic ester or acid group,when the carboxylic acid group and the boronic ester or acid group isbonded, respectively, to an alkyl, i.e., sp³ hybridized, carbon atom.

An alkyl carboxylic acid compound RCO₂H, as the term is used herein, isa compound that has a carboxylic acid, —CO₂H, group bonded to an alkylcarbon atom, i.e., an sp³ hybridized carbon atom. Other parts of themolecule can comprise aryl or heteroaryl rings, heteroaroms,unsaturations, and other functional groups, as well as other alkylcarbon atoms.

An alkyl boronic acid compound, RB(OH)₂, as the term is used herein, isa compound that has a boronic acid, —B(OH)₂, group bonded to an alkylcarbon atom, i.e., an sp³ hybridized carbon atom. Other parts of themolecule can comprise aryl or heteroaryl rings, heteroaroms,unsaturations, and other functional groups, as well as other alkylcarbon atoms.

A pinacolato ester of an alkyl boronic acid is of formula

and both the ester and the acid boronate structures can comprise thesame R group unchanged from the R group of the carboxylic acid RCO₂H.Consequently, the reaction is very chemoselective for a carboxylic acidsubstrate, tolerating a wide range of chemical functionality elsewherein the molecule. Because a boronic acid group is a pharmaceuticallyinteresting isosteric replacement for a carboxylic acid group, thischemoselectivity allows a wide range of pharmaceuticals that contain acarboxylic acid group to be converted to the corresponding boronic acidcompounds without disruption of functional groups elsewhere in themolecule.

The invention in its various embodiments provides the followingadvantages in carrying out the transformation described, that replaces acarboxylic acid group with a boronic acid group under conditions thatare selective, mild, and cost effective. Some of the advantages ofpracticing a method of the invention include: Practicality: theinvention uses inexpensive reagents with minimal precaution. Therefore,it can be readily adopted in both discovery and process settings. Broadscope: carboxylic acids which are amongst the most ubiquitous functionalgroups in commercial chemicals and pharmaceuticals are used in thistransformation. The reaction also exhibits high chemoselectivity,thereby can be readily used to diversify a broad array of substrates.Urgency: there is increasing awareness of the importance of boronicacids in drug discovery but effective and general methods of boronicacid synthesis are lacking. This invention fills up this gap inmethodology.

The invention provides, in various embodiments, a method of convertingan alkyl carboxylic acid compound RCO₂H to a corresponding alkyl boronicpinacolato ester compound

wherein R is a hydrocarbyl group comprising an sp³ hybridized carbonatom bonded to the CO₂H or the boron atom, respectively, R optionallyfurther comprising alkyl or alkyenyl groups, both optionally comprisingheteroatoms, or optionally comprising aryl, heterocyclyl, or heteroarylgroups, or any combination thereof;

the method comprising:

a) forming a redox active ester (RAE) of the alkyl carboxylic acidcompound; then,

b) contacting the redox active ester of the alkyl carboxylic acidcompound in an aprotic solvent, and bis(pinacolato)diboron (B₂pin₂), inthe presence of at least 20 mole % of a Mg(II) salt and of at least onemolar equivalent a lithium compound comprising a (C1-C4)alkyllithium, a(C1-C4)alkoxylithium, or lithium hydroxide, and at least 10 mole % of aCu or Ni salt;

in the presence of a 1,3-dicarbonyl ligand forming with the Cu acompound of formula (M)

wherein R_(1A) and R_(2A) are each independently selected (C1-C4)alkyl,trifluoromethyl, or phenyl;

or in the presence of a ligand of formula (L) comprising a bipyridyl offormula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl;

to provide the corresponding alkyl boronic pincolato ester compound.

More specifically, the invention provides, in various embodiments, amethod of converting the alkyl carboxylic acid compound to thecorresponding alkyl boronic pinacolato ester compound, comprising:

a) forming the redox active ester (RAE) of the alkyl carboxylic acidcompound; then,

b) either: 1) contacting in aprotic solvent the redox active ester, atleast one molar equivalent bis(pinacolato)diboron (B₂pin₂), andeffective amounts of a Mg(II) salt in the present of lithium hydroxideor a lithium (C1-C4)alkoxide, and in the presence of a Cu(I) or a Cu(II)complex or both of a 1,3-dicarbonyl compound, the complex being offormula (M)

wherein R_(1A) and R_(2A) are each independently selected (C1-C4)alkyl,trifluoromethyl, or phenyl,

or in the presence of a Cu(I) or a Cu(II) salt or both and an effectiveamount of a ligand (L) comprising a bipyridyl of formula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl;

or: 2) contacting in aprotic solution the redox active ester andeffective amounts of a Ni(II) salt and a Mg(II) salt, in the presence ofan effective amount of a ligand (L) comprising a bipyridyl of formula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl;

then, adding a premixed solution comprising at least one molarequivalent of an organolithium compound and at least one molarequivalent bis(pinacolato)diboron (B₂pin₂);

to provide the pinacolato ester of the corresponding alkyl boronic estercompound.

More specifically, in carrying out a method of the invention, the redoxactive ester of the alkyl carboxylic acid can be an N-hydroxyphthalimide(NHPI) or can be a tetrachloro-N-hydroxyphthalimide (TCNHPI) ester.

More specifically, in carrying out a method of the invention, for theCu-catalyzed reaction the Cu(II) salt can be Cu(acac)₂, or for theNi-catalyzed reaction the Ni(II) salt can be NiCl₂.

More specifically, in carrying out a method of the invention, the Mg(II)salt can be MgBr₂ or Mg Cl₂.

More specifically, in carrying out a method of the invention, for theCu-catalyzed reaction the lithium compound can be LiOH or a lithium(C1-C4)alkoxide, or for the Ni-catalyzed reaction the organolithiumcompound can be methyllithium.

More specifically, in carrying out a method of the invention, theaprotic solvent can comprise THF or dioxane, and DMF.

The invention further provides, in various embodiments, the methoddisclosed above, further comprising step c) cleaving under acidicconditions the pinacolato ester of the alkyl boronic acid compound

to provide the alkyl boronic acid compound RB(OH)₂. For instance, thestep of cleaving the pinacolato ester of the alkyl bornic acid compoundcan comprise contacting the ester with BCl₃ followed with methanol, orcontacting the ester with trifluoroacetic acid, or contacting the esterwith a boronic acid, such as phenylboronic acid or 2-methylpropylboronicacid in aqueous HCl.

In various embodiments of the invention, the ligand (L) can be abipyridyl of formula L1-L5

wherein

R₁=OMe, R₂=H, L1

R₁=tBu, R₂=H, L2

R₁=H, R₂=H, L3

R₁=Me, R₂=H, L4

R₁=OMe, R₂=OMe, L5;

or the ligand (L) can be a 1,10-phenanthroline of formula L7-L9

wherein

R₃=H, R₄=H, L7

R₃=Ph, R₄=H, L8

R₃=OMe, R₄=H, L9.

In various embodiments of the reaction, the Cu ligand of formula (M) canbe

wherein each R_(1A) and R_(2A) is independently selected (C1-C4)alkyl,trifluoromethyl, or phenyl.

For example, the invention provides in various embodiments a method ofpreparation of alkyl boronic compound ninlaro (1)

from alkyl carboxylic acid compound:

by carrying out the steps a), b), and c) as disclosed above.

For example, the invention provides in various embodiments a method ofpreparing a boronate ester analog of atorvastatin ketal, comprising,first, a) forming the N-hydroxyphthalimide (NHPI) ester of atorvastatinketal to provide redox active ester

then, carrying out step b) disclosed above, to provide the boronateester of the analog of atorvastatin ketal

The invention further provides, as a composition of matter, a boronateester analog of atorvastatin ketal of formula

The invention further provides, as a composition of matter, a boronicacid analog, freed of the pinacolato ester group, of atorvastatin ketalof formula

For example, the invention provides in various embodiments a method ofpreparing a dimethyl-t-butylsilyl (TBS) hydroxyl-protected boronic acidanalog of a vancomycin aglycone

comprising, first, a) converting the carboxylic acid

to the corresponding NHPI redox activated ester, then carrying out stepb), above, to provide an O-protected boronate pinacolato ester of theboronic acid, then carrying out step c), above, cleaving the boronicester group to provide the O-protected boronic acid compound of formula

The invention further provides, as a composition of matter, ahydroxyl-protected boronic acid analog of a vancomycin aglycone

wherein TBS signifies a dimethyl-t-butylsilyl O-protecting group.

The invention also provides, as a method and as a composition of matter,a boronic acid analog of vancomycin aglycone of formula

prepared by cleavage of the t-butyldimethylsilyl (TBS) esters of the twoprotected hydroxyl groups using standard synthetic conditions such astris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) in DMF.

For example, the invention provides in various embodiments a method ofpreparing boronic acid mCBK319 elastase inhibitor compound

comprising carrying out steps a), b), and c) as described above startingwith carboxylic acid compound

The invention further provides, as a composition of matter, a boronicacid mCBK319 (50) elastase inhibitor compound of formula

For example, the invention provides in various embodiments a method ofpreparing the Boc-protected boronic ester compound of formula

comprising carrying out step b), above, on compound

to provide the Boc-protected boronic pinacolato ester compound

In additional embodiments, the Boc-protected boronic pinolcolato estercompound

can further undergo cleaving the Boc group of the compound withtrifluoroacetic acid, followed by condensation of the resulting freeamino group with compound

followed by cleavage of the pinacolato boronate ester group withphenylboronic acid in aqueous HCl to provide the boronic acid mCBK320(51) elastase inhibitor compound of formula

The invention further provides, as a composition of matter, a boronicacid mCBK320 elastase inhibitor compound of formula

In further embodiments, the above Boc-protected boronic pinolcolatoester compound can further undergo cleaving the Boc group and of theboronate ester of the compound with trifluoroacetic acid, followed bycondensation of the resulting free amino group with a compound offormula

followed by cleavage of the t-Bu ester,to provide a boronic acid compound of formula (mCBK323 elastaseinhibitor, 53)

The invention further provides, as a composition of matter, a boronicacid compound of formula (mCBK323, elastase inhibitor)

The invention further provides, in various embodiments, a method ofpreparation of an arylomycin sidechain analog boronic acid

comprising carrying out the conversions comprising steps a), b) and c)as described above, followed by removal of the N-Boc groups with acid,starting with an arylomycin sidechain analog carboxylic acid of formula

The invention also provides, as a novel composition of matter, anarylomycin sidechain analog boronic acid of formula

The invention further provides, in various embodiments, a method ofsynthesis of a Cyclic Boronic Acid β-Lactamase Inhibitor (RPX7009), offormula

and related boronic acid analogs, see “Discovery of a Cyclic BoronicAcid β-Lactamase Inhibitor (RPX7009) with Utility vs Class A SerineCarbapenemases” by Scott J. Hecker, et al., DOI:10.1021/acs.jmedchem.5b00127, J. Med. Chem. (2015), 58, 3682-3692. A keyintermediate in the synthesis of β-Lactamase Inhibitor (RPX7009),Hecker-9f, and analogs as described in the cited article, is compoundHecker-12 therein,

wherein TBDMS signifies a t-butyldimethylsilyl protecting group. Thiskey intermediate can be prepared according to a method of the presentinvention from a compound of formula

the preparation of which is described in racemic form in publication M.Ghosh, M. J. Miller, Tetrahedron, 1996, 52, 4225. Use of a borylationmethod of the invention can yield compound Hecker-12 from thiscarboxylic acid intermediate. Methods to effect stereoselectivereduction of beta-ketoesters to yield a chiral alcohol are well known tothose skilled in the art, e.g. chiral borohydride reagents, or aruthenium catalyzed asymmetric hydrogenation reaction, providing theGhosh carboxylic acid in chiral form. For instance, the preparation ofthe carboxylic acid precursor for the borylation reaction of theinvention can be prepared according to the following route:

The remainder of the synthesis can be carried out as described inHecker, where use of a chiral pinanediol in the boronate ester exchangereaction of compound Hecker—12 to yield chiral Hecker—13 (see Scheme 1of Hecker, et al.) can provide intermediates of good enantiomericpurity. These intermediates can be used in the preparation of all ofβ-Lactamase Inhibitors such as RPX7009, compounds Hecker-9a throughHecker-9r (see Table 1 of Hecker et al. publication).

See also related documents: “Reaktion von a-Lithioessigsaureestern mitBernsteinsaureanhydriden” Von Franz-Peter Montforts und Silvio Ofner,Angew. Chem. (1979) 91, no. 8, p. 656; “Highly EnantioselectiveHydrogenation of β-Keto Esters under Mild Conditions” Mark J. Burk,* T.Gregory P. Harper, and Christopher S. Kalberg, (1995) J. Am. Chem. Soc.,117, 4423-4424; and “Asymmetric Hydrogenation of α-Keto CarboxylicEsters. A Practical, Purely Chemical Access to α-Hydroxy Esters in HighEnantiomeric Purity” R. Noyori,* T. Ohkuma, and M. Kitamura (1987), J.Am. Chem. Soc., Vol. 109, No. 19, 5856.

While the invention has been described and exemplified in sufficientdetail for those skilled in this art to make and use it, variousalternatives, modifications, and improvements will be apparent to thoseskilled in the art without departing from the spirit and scope of theclaims.

Standard abbreviations for chemical groups such as are well known in theart are used; e.g., Me=methyl, Et=ethyl, i-Pr=isopropyl, Bu=butyl,t-Bu=tert-butyl, Ph=phenyl, Bn=benzyl, Ac=acetyl, Bz=benzoyl, and thelike.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B. Development of the decarboxylative borylation reaction.(FIG. 1A) Carboxylic Acids to Boronic Acids: Strategic Value. (FIG. 1B)Decarboxylative Borylation: Invention and Optimization.

FIGS. 2A and 2B. Scope of the Ni-catalyzed decarboxylative borylationreaction of redox-active esters. FIG. 2A Standard Reaction conditions:Redox active NHPI ester (1.0 equiv), NiCl₂.6H₂O (10 mol %), L1 (13 mol%), MgBr₂.OEt₂ (1.5 equiv), B₂pin₂ (3.3 equiv), MeLi (3.0 equiv),THF/DMF (2.5:1), 0° C.-RT, 2 h; examples of primary and secondaryboronates; FIG. 2B examples of tertiary boronates and natural products.

FIGS. 3A, 3B and 3C. Applications of the decarboxylative borylationreaction. (FIG. 3A) Decarboxylative borylation enabled late-stagediversification of Lipitor. (FIG. 3B) Synthesis and biologicalevaluation of a borono-vancomycin analog. (FIG. 3C) Synthesis andbiological evaluation of human Elastase inhibitors.

FIGS. 4A and 4B. Discovery of novel human neutrophil elastase (HNE)inhibitors, FIG. 4A compounds tested; FIG. 4B inhibitory activities ofHNE inhibitors 50-58 as a function of concentration.

DETAILED DESCRIPTION

In this report, a simple method for nickel-catalyzed decarboxylativeborylation is presented that is mild, scalable, and general across arange of primary, secondary, tertiary, peptidic, and even naturallyoccurring substrates. A diverse array of boronates which would otherwiserequire lengthy de novo synthesis were furnished directly from thecorresponding carboxylic acids. This method's capacity to directlytransform native peptides into α-amino boronic acids has led to thediscovery of three potent small molecule elastase inhibitors.

Recent efforts in our laboratory revealed redox active esters (RAEs,e.g., N-hydroxyphthalimide ester 2) derived from alkyl carboxylic acidsas convenient surrogates for alkyl halides in nickel or iron catalyzedcross-coupling reactions. These versatile intermediates, most commonlyused in amide-bond forming reactions, have enabled practical means ofC—C bond formation in various modalities, including decarboxylativeNegishi (22-23), Suzuki (24), and Kumada (25) couplings, as well asGiese reactions (26). Although RAEs have yet to be used incarbon-heteroatom cross-coupling reactions, our earlier discoveries,coupled with Fu's (10) pioneering work on nickel catalyzed Miyauraborylation of alkyl halides (11-14), prompted us to investigate thepossibility of harnessing them for C—B bond formation, thereby achievingdirect conversion of alkyl carboxylic acids into boronic acidderivatives.

Realization of this seemingly straightforward transformation requiredconsiderable experimentation. FIG. 1B provides the optimal reactionparameters alongside an abbreviated picture of the optimization processon 2-methyl-4-phenylbutanoic acid. The simple NHPI ester (2) proved tobe the optimal substrate for borylation with bis(pinacolato)diboron

(B₂pin₂);

other RAEs such as the tetrachloro-NHPI ester were less effective (entry1). The inexpensive combination of NiCl₂.6H₂O and bipyridine ligand L1emerged as the best catalyst system after an exhaustive screening—use ofalternative catalysts (see SI) or ligands (entries 3-5) have deleteriouseffects. Choice of solvent is critical: a binary mixture of THF and DMFgave the optimal result; lower yields were observed in the absence ofDMF (entry 6). Pre-mixing methyl lithium with B₂pin₂ is necessary toactivate the diboron species toward transmetalation; numerous otherorganometallic reagents surveyed (e.g., entries 8-10) were lesseffectual, affording borylation products in lower yields if at all.Magnesium salts were also indispensable to the reaction: in the absenceof the MgBr₂.OEt₂, virtually no products were attained (entries 11-13).Borono-ester product 3 can be accessed directly from the carboxylic incomparable yields using a one-pot procedure wherein RAE 2 is formed insitu in a similar vein to amide coupling (entry 14). Overall, thereaction proceeds smoothly at room temperature over the course of 2hours.

With the optimized conditions in hand, the scope of this methodology wassubsequently explored. RAEs derived from a broad selection of primary,secondary, and tertiary carboxylic acids were all found to be viablesubstrates (FIG. 2). These encompass acyclic, cyclic, caged, bridgehead,fluoroalkyl, and benzylic acids which were transformed to thecorresponding Bpin boronate esters smoothly. Scalability of the reactionis evident through the preparation of 29 on a gram scale. Additionally,12 of the products (3, 4, 7, 11, 12, 13, 16, 19, 25, 29, 35, 38) wereobtained in comparable yields when only 2.5 mol % of nickel catalyst(3.3 mol % of ligand) was used, further attesting to the adaptability ofthis method in a process setting.

As the methyl lithium was pre-mixed with B₂pin₂ to form ate-complexes,strongly nucleophilic/basic organometallic species were sequestered fromthe substrate: a gamut of functionalities such as ethers (30, 31, 35,37, 41), esters (5, 8, 21, 22, 39, 41), carbamates/amides (8, 15, 28,36, 37, 1), ketones (34, 38, 39, 40), olefins (39, 40, 41), and hydroxyl(40, 41) were left unscathed under the mild reaction conditions. Indeed,even the highly base-sensitive Fmoc group was tolerated (see 8). Thecompatibility with alkyl bromides (7) and chlorides (33) points to theorthogonality of this reaction to halide-based Miyaura borylations.Enoxolone derived boronates 39 and 40 were obtained with similar yields,suggesting that the free hydroxyl group had minimal influence on thereaction. The discrete isolation of RAEs, as alluded to earlier, is notnecessary. Tertiary and secondary boronate esters can be prepareddirectly from carboxylic acids when RAEs are generated in situ. Thisone-pot procedure also pertains to primary substrates, albeit at loweryields.

Although some of the products presented herein (e.g., 4, 17, 19, 20, 23)can be synthesized from the analogous halides via Miyaura borylationreactions, the starting organohalides are oftentimes not commerciallyavailable and require extraneous steps to prepare (usually from thecorresponding alcohols). Conversely, the use of readily availablecarboxylic acids largely circumvents this problem. A great majority ofproducts in FIG. 2 are derived directly from commercially availableacids. For instance, 21 was conveniently prepared from a cubane-basedcarboxylic acid whereas the reported synthesis of the analogous halideenlisted a harsh Hundsdiecker reaction (Br₂ and HgO) on the same acid(29). Furthermore, the scope of this borylation protocol can be extendedto amino acid derivatives to furnish α-amino boronate esters such as 15.Synthesis of 15 through halide-based Miyaura borylation is simply notfeasible as the corresponding α-amino halide starting material would beunstable. In this regard, the decarboxylative borylation strategy allowsexplorations of previously elusive chemical space

The prevalence of alkyl carboxylic acids is demonstrated by theirpresence in over 450 approved drug molecules (30). To this end, theimpressive chemoselectivity of this reaction offers the uniqueopportunity to pursue late-stage modifications of bioactive moleculesthat are densely adorned with reactive functionalities. Over 10carboxylate containing drug molecule/natural products have beensuccessfully converted into pinacol boronate esters (28-41) which wouldotherwise only be accessible through multi-step functional groupinterconversions or de novo syntheses.

The boronate esters can be conveniently hydrolyzed into thecorresponding boronic acids (e.g., 4a, 3a, 33a, 1) (FIG. 2). This allowsthe transformation of bioactive carboxylic acids into theirborono-bioisoteres to identify compounds with superior potency orpharmacokinetic properties. Alternatively, boronate esters could bediversified into a variety of structural motifs (31-33). As anillustrative example, the Lipitor derived Bpin ester (36) can beexpediently elaborated into the corresponding alcohol (36a) or carbamate(36b) (34) upon treatment with appropriate oxidants (FIG. 3A). Underconditions reported by Aggarwal, 36c and 36d were directly accessedthrough reaction with aryllithium species (35). Decarboxylativeborylation could also convert RAEs, which are electrophiles incross-couplings, into Bpin esters that serve as nucleophiles in Suzukireactions (e.g., 36 to 36e and 36 to 36f) (36). This “umpolung” approachis particularly strategic in the case of 36e whereby the2-pyridylboronic acid or organozinc species are often not viable Suzukisubstrates owing to a lack of stability.

Moreover, selective decarboxylative borylation at the C-terminus ofnative peptides allowed rapid access to coveted α-amino boronic acidswhich are privileged medicinal chemistry motifs (18, 37). Ninlaro (1),for example, was obtained in three steps from a simple peptide (FIG. 2).This opens up a distinct dimension to the study of peptide-basedtherapeutics: in perhaps the most striking example, vancomycin wasconverted into a boronic acid analogue (44) through the decarboxylativeborylation of 42 (FIG. 3B) (38).

This process proceeded smoothly in the presence of four methylatedphenoxy groups, two TBS-protected hydroxyls, two aryl chlorides, sixsecondary amides, one primary amide, one secondary amine, and sevenepimerizable stereocenters. Although 44 showed less activity compared tothe parent acid 43, such remarkable chemoselectivity still attests tothe potential utility of this reaction.

Unpredictable stereoselectivity of radical processes oftentimes presentsa hurdle to their broad adoption in late-stage modifications of drugleads or natural products. Complex α-amino boronic acid 44 was obtainedas a single diastereomer in this radical-based decarboxylativeborylation reaction. This result prompted us to investigate thestereoselectivity of the decarboxylative borylation on severaldipeptides (FIG. 3D). We found that increased steric bulk on theN-terminal residue resulted in better diastereoselectivity: though bothdiastereomers were furnished in almost equal quantities for 45, higherselectivities were observed for 46 and 47. Meanwhile, 46 was obtained inthe same diastereomeric ratio from Boc-l-Val-l-Val and Boc-l-Val-d-Val.Lower reaction temperatures could also be used to enhance thestereoselectivity. At −15° C., 48 was furnished in greater than 5 to 1d.r., enabling a stereoselective synthesis of Velcade (49) in a shortsequence.

By wedding the rich medicinal potential of boronates to the ubiquity ofalkyl carboxylic acids, the decarboxylative borylation reaction has thepotential to open up new vistas in drug development. For example,application of the decarboxylative borylation reaction to readilyavailable dipeptides allowed the expedient preparations of 50-52 whichwere formed as single diastereomers and found to be potent inhibitors ofhuman neutrophil elastase (HNE) (FIGS. 4A and B). Notably, thecarboxylic acid precursor to 50 (50b) was found to be devoid of anyinhibitory activities while 50 and 51 displayed substantially enhancedpotency compared to their trifluoroketones congeners (50a and 51a),which have been examined in phase II clinical trials for lung diseasessuch cystic fibrosis (39-45). HNE, a highly active serine protease,plays a pivotal role in the immune response, tissue remodelling, and theonset/resolution of inflammation by breaking down mechanically importantstructures of the body's cellular matrix as well as proteins of foreignorigin (46). While five generations of HNE inhibitors have beenevaluated clinically in multiple inflammatory lung diseases (e.g.,cystic fibrosis, emphysema, and bronchiectasis), none have beenoverwhelmingly efficacious in humans to make a significant impact inthese conditions (46).

Toward this end, 52 exhibited an ICo₅₀=15 pM (Ki=3.7 pM) while 51exhibited an IC₅₀=30 pM (Ki=34 pM) against purified HNE. The IC₅₀ valueswere determined head-to-head with other pre-clinically and clinicallyvalidated HNE inhibitors (53-57), including BAY 85-8501 (54, a leadingclinical candidate with reported Ki=80 pM) (47), 55 (POL6014, a phase Ipeptide-based clinical candidate for cystic fibrosis) (48) as well as 56and 57 (reported by Chiesi Pharmaceuticals) (49). Additionally, 51 and52 retained much of their inhibitory activities in sputum samples ofcystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD)patients, underscoring their potency in the context of a morepatho-physiologically relevant environment than the traditionalbiochemical assay. Conversely, while dimeric compound 58 fromAstraZeneca (IC50=11 pM, Ki=2.7 pM) (50), and BAY 85-8501 (54) showcasedlow IC₅₀ values, their potencies diminished drastically in patientderived sputum. Comparison of the LipE values in COPD sputum revealedthat the superior potency of 52 is not driven by increased lipophilicity(10.2 versus 9.45 for 57) (51).

Additionally, the IC₅₀ value of 52 was found to remain unchanged withincreasing incubation times (between 5-60 minutes) while that of 58, anon-covalent inhibitor exhibited a 55-fold increase in potency under thesame conditions. These data retain the profile that is expected:compound 52 is behaving like a partial mechanism-based inhibitor (or acovalent reversible inhibitor) likely due to the potentially slowoff-rate of the α-amino boronic acid. This correlates with tighterbinding and potentially long residence time seen in other amino boronicacid compounds unlike the many reversible elastase inhibitors (i.e. 58)(52). Clinically, this mechanism has been proven successfully throughVelcade (49), which inhibits the catalytic site of the 26Sproteasome-covalent reversible bonding between the boronate and thenucleophilic oxygen results in a slow disassociation rate (53-54). Asmost clinical elastase inhibitors (such as 54, BAY 85-8501, one of themost potent molecules reported to date) are non-reactive, reversible,transition state inhibitors, 52's high potency and the inherentmechanism of the amino boronic acids could help address theselimitations. Through this “hybrid” enzymatic inhibitory approach (basedupon Fischer's Lock and Key model/Ehrlich's Pharmacophore Model),boronic acids such as 52, which combine a rapid, potent binding with aslow off-rate, may effectively restore the protease versus anti-proteasebalance in a clinical setting. They could therefore be tuned towardlung-specific clinical applications rapidly.

To further evaluate the therapeutic potential of 51 and 52, the in vitroADME properties were probed to determine if any deleterious effects ofthe boronate replacements of the ketone would be revealed (FIG. 4C).These amino boronic acids displayed comparable kinetic solubility to thetrifluoromethyl ketone analog (51a). A substantial portion (90% and 79%respectively) of 51 and 52 were found to be intact in CD-1 mouse plasmaover 2 hours. 51 and 52 exhibited similar metabolic stability as thetrifluoroketone 51a. 51 and 51a also demonstrated similar levels ofpermeability in Caco-2 cells (See Page 176 of the supplementaryinformation). These data suggest that the novel boronates simply improvepotency without changing the drug-like properties of their ketonecongeners.

Method Summary:

Procedurally, the conversion of redox active esters into boronate estersis achieved in three stages: namely, the preparation of catalystmixture, the preparation of [B₂pin₂Me]Li complex and the nickelcatalyzed decarboxylative borylation reaction. An abbreviatedexperimental protocol is presented herein with a graphical guide.Comprehensive information on the commercial source and purity ofchemicals or variations in experimental details for different substrateclasses can be found in the supplementary information.

Preparation of NiCl₂.6H₂O/Ligand Stock Solution or Suspension:

A flask charged with NiCl₂.6H₂O (1.0 equiv.) and ligand (L1 or L2, 1.3equiv.) was evacuated and backfilled with argon for three times. THF(the concentration of NiCl₂.6H₂O was 0.025 M) or DMF (the concentrationof NiCl₂.6H₂O was 0.050 M) was added. The resulting mixture was stirredat room temperature overnight (or until no granular NiCl₂.6H₂O wasobserved) to afford a green solution or suspension. [Note: All thesolutions or suspensions kept under argon can be used for several dayswithout appreciable deteriorations in reaction yields.]

Preparation of [B₂Pin₂Me]Li Complex:

To a solution of B₂pin₂ (1.1 equiv.) in THF (the concentration of B₂pin₂was 1.1 M) was added MeLi (1.6 M in Et₂O, 1.0 equiv.) at 0° C. underargon. The reaction mixture was warmed to room temperature and stirredfor 1 h to afford a milky white suspension.

Ni-Catalyzed Decarboxylative Borylation:

A flask charged with the redox-active ester (1.0 equiv.) and MgBr₂.OEt₂(1.5 equiv.) was evacuated and backfilled with argon for three times.Catalyst solution or suspension (containing 10 mol % of NiCl₂.6H₂O and13 mol % of ligand) was added via a syringe. When a catalystsuspension/solution in DMF was used, an additional portion of THF (twicethe volume of the DMF suspension/solution needed) was added to thereaction vessel prior to the addition of the catalyst mixture [thisprocess can be exothermic on large scales and cooling (with ice/waterbath) may be necessary]. The resulting mixture was stirred vigorouslyuntil no visible solid was observed at the bottom of the reaction vessel[this was found to be accelerated by sonication]. This mixture wascooled to 0° C. before a suspension of [B₂pin₂Me]Li in THF (3 equiv.)was added in one portion. After stirring for 1 hour at 0° C., thereaction was warmed to room temperature and stirred for another 1 hour.When thin layer chromatography (TLC) analysis indicated the completionof the reaction, the reaction was quenched with aqueous HCl (0.1 M) orsaturated aqueous NH₄Cl and extracted with diethyl ether (Et₂O) or ethylacetate (EtOAc). Alternatively, on larger scales, as is the case shownin FIG. 5, the reaction mixture was directly poured onto Et₂O and theresulting suspension was filtered through a pad of silica gel andcelite. Purification by column chromatography afforded the desiredboronate ester.

Through the exclusive use of N-hydroxy-phthalimide redox active esters,a simple means to interconvert two functional groups of paramountimportance in organic chemistry has been enabled. The practicality andchemoselectivity are illustrated through numerous complex substratesincluding drug molecules. The broad scope, epitomized by the ability todirectly transform native peptides into borono-isosteres in goodstereoselectivities, is unmatched by halide-based Miyaura-Suzukiprotocols. Alkyl boronates can be introduced at any stages of asynthesis, reshaping the strategic paradigm toward their preparations.By wedding the rich medicinal potentials of boronates to the ubiquity ofalkyl carboxylic acids, this method will likely open up new vistas indrug development. This is already evident from the discovery of mCBK320, a highly potent elastase inhibitor with potentials in cancertherapy.

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EXAMPLES Boronic Acid Inhibitors of Human Neutrophil Elastase Preparedby Method of the Invention Compounds for Disclosure (IC₅₀ on HumanNeutrophil Elastase)

Synthetic Routes to Boronic Acid Inhibitors of Human Neutrophil Elastase

Preparation of mCBK319

Preparation of mCBK320 and mCBK323

All three compounds (mCBK319, mCBK320, and mCBK323) were found topossess a high propensity toward trimerization at the boronic acidmotif. The bioactivities of these trimers may warrant furtherinvestigations. These novel elastase inhibitors have potentialapplications as therapeutics for cancer, cycstic fibrosis, andbronchiectasis.

The compounds have displayed enhanced potency compared to lead compoundsscreened (100-1000 fold increase compared to the analogoustrifluoroketone lead compounds) as elastase inhibitors. The uniquephysiochemical properties of the boronic acid motif may give rise tofavorable pharmacokinetic attributes. The processes for preparationdisclosed herein are concise and easily amenable for scale up.

General Information

Tetrahydrofuran (THF), N,N-dimethylformamide (DMF), acetonitrile (CH3CN)dichloromethane (CH2Cl2) were obtained by passing the previouslydegassed solvents through activated alumina columns. Other solvents andreagents were purchased at the highest commercial quality and usedwithout further purification, unless otherwise stated.

Yields refer to chromatographically and spectroscopically (1H-NMR)homogeneous material, unless otherwise stated. Reactions were monitoredby GC/MS, LC/MS, and thin layer chromatography (TLC). TLC was performedusing 0.25 mm E. Merck silica plates (60F-254), using short-wave UVlight as visualizing agent, as well as potassium permanganate (KMnO₄) orceric ammonium molybdate (CAM) and heat as developing agents. NMRspectra were recorded on Bruker DRX-600, DRX-500 or DPX-400 instrumentsand are calibrated using residual undeuterated solvent (1H: δ 7.26 forCDCl3, δ 3.31 for MeOH-d4, δ 3.58, 1.73 for THF-d8, δ 2.50 for DMSO-d6,δ 2.05 for acetone-d6; 13C: δ 77.16 for CDCl3, δ 49.0 for MeOH-d4, δ67.6, 25.5 for THF-d8, δ 39.50 for DMSO-d6, δ 29.84 for acetone-d6). Thefollowing abbreviations were used to explain multiplicities: s=singlet,d=doublet, t=triplet, q=quartet, m=multiplet, br=broad. Columnchromatography was performed using E. Merck silica gel (60, particlesize 0.043-0.063 mm), and preparative TLC was performed on 0.25 mm E.Merck silica plates (60F-254). High resolution mass spectra (HRMS) wererecorded on an Agilent LC/MSD TOF mass spectrometer by electrosprayionization time of flight reflectron experiments. Preparative highperformance liquid chromatography (HPLC) was performed using an AgilentSD-1 prepstar system equipped with Phenomenex Gemini 10 μm C18 columnwith dimension 200×50 mm. Melting points were recorded on a Fisher-Johns12-144 melting point apparatus and are uncorrected. All X-raydiffraction data were collected and analyzed by the UCSD small moleculeX-ray facility. The deactivated silica gel (35 wt % H₂O) was prepared bymixing silica gel and deionized water, followed by vigorous shakinguntil a fluffy powder was observed.

B₂pin₂ is bis(pinacolato)diboron.

NHPI is N-hydroxyphthalimide. TCNHPI istetrachloro-N-hydroxyphthalimide. Standard abbreviations for chemicalgroups such as are well known in the art are used; e.g., Me=methyl,Et=ethyl, i-Pr=isopropyl, Bu=butyl, t-Bu=tert-butyl, Ph=phenyl,Bn=benzyl, Ac=acetyl, Bz=benzoyl, TBS=dimethyl-t-butylsilyl,Boc=t-butoxycarbonyl, and the like.

Preparative HPLC was performed using an Agilent SD-1 prepstar systemequipped with Phenomenex Gemini 10 μm C18 column with dimension 200×50mm. Melting points were recorded on a Fisher-Johns 12-144 melting pointapparatus and are uncorrected. All X-ray diffraction data were collectedand analyzed by the UCSD small molecule X-ray facility. The deactivatedsilica gel (35 wt. % H2O) was prepared by mixing silica gel anddeionized water, followed by vigorous shaking until a fluffy powder wasobserved.

General Procedure for the Synthesis of Redox-Active Esters (RAEs)(General Procedure A)

A round bottom flask was charged with the carboxylic acid (1.0 equiv),N-hydroxyphthalimide (NHPI, 1.0 equiv) ortetrachloro-N-hydroxyphthalimide (TCNHPI, 1.0 equiv) and DMAP (0.1equiv). CH2Cl2 (0.2 M) was added, followed byN,N′-diisopropylcarbodiimide (DIC, 1.1 equiv), both at room temperature.The mixture was allowed to stir at room temperature until all the acidwas consumed (as indicated by TLC). The resulting mixture was quicklyfiltered and the solid residue was rinsed with more CH2Cl2. The filtratewas concentrated in vacuo and purified by flash column chromatography toafford the corresponding redox-active esters, which were used withoutfurther purification unless otherwise noted.

Optimization Details

All reactions were screened based on 0.1 mmol scale. The optimizationstarted with S1. TCNHPI esters were used in the initial screening sinceearlier conditions indicated better performance than NHPI esters (NHPIesters were used in the optimized conditions in the end.

TABLE 1

RAEs Yield* X = H 31% X = Cl 45% *Yields determined by GC-FID withdodecane as internal standard.

TABLE 2

Base Yield* w/o base  0  MeLi 58% (54%^(†)) MeLi·LiBr 58% nBuLi 45%tBuLi 36% MeMgBr 11% MeMgBr (w/o MgBr₂)  7% EtMgBr 10% EtOK  0  tBuOK 0  MeOLi  0  NaHMDS  0  KHMDS  0  LiHMDS  0  KF  0  CsF  0  *Yieldsdetermined by GC-FID with dodecane as internal standard. ^(†)Isolatedyield.

TABLE 3

Additive (equiv.) Yield* w/o  4% Mg(OAc)₂ (1.5 equiv.) <1% Mg(acac)₂(1.5 equiv.) <1% MgCl2 (1.5 equiv.) 13% MgSO₄ (1.5 equiv.) <1% LiBr (3.0equiv.) 34% ZnCl₂ (1.5 equiv.) 14% MgBr₂·OEt₂ (0.2 equiv.) 23%MgBr₂·OEt₂ (0.6 equiv.) 53% MgBr₂·OEt₂ (1.0 equiv.) 64% MgBr₂·OEt₂ (1.5equiv.) 67% (63%^(†)) MgBr₂·OEt₂ (2.0 equiv.) 66% MgBr₂·OEt₂ (2.5equiv.) 57% *Yields determined by GC-FID with dodecane as internalstandard. ^(†)Isolated yield.

TABLE 4

Nickel source Yield* NiCl₂ ^(·6)H₂O 67% (63%^(†)) NiCl₂·glyme 58%NiBr₂·glyme 63% NiI₂ 14% Ni(acac)₂·2H₂O 17% Ni(ClO₄)₂  3% Ni(PCy)₃Cl₂ 4% w/o nickel  0  *Yields determined by GC-FID with dodecane asinternal standard. ^(†)Isolated yield.

TABLE 5

Ligand Yield* L2 67% (63%^(†)) L2 (20 mol %) 57% L1 51% L3 23% L4 26% L5 4% L6  0  L7 13% L8 11% L9 17% L10  0  L11  0  L12  1% L13  1% L14  0 L15  1% L16  1% w/o ligand  0  *Yields determined by GC-FID withdodecane as internal standard. ^(†)Isolated yield.

TABLE 6

B₂pin₂ (equiv.), MeLi (equiv.) Yield* B₂pin₂ (2.2 equiv.), MeLi (2.0equiv.) 51% B₂pin₂ (2.75 equiv.), MeLi (2.5 equiv.) 65% B₂pin₂ (3.3equiv.), MeLi (3.0 equiv.) 67% (63%^(†)) B₂pin₂ (3.85 equiv.), MeLi (3.5equiv.) 60% B₂pin₂ (4.4 equiv.), MeLi (4.0 equiv.) 57% *Yieldsdetermined by GC-FID with dodecane as internal standard. ^(†)Isolatedyield.

TABLE 7

Concentration Yield* 0.025 M 44% 0.033 M 58%  0.05 M 67%  0.10 M 67%(63%^(†))  0.15 M 65% *Yields determined by GC-FID with dodecane asinternal standard. ^(†)Isolated yield.

However, under the aforementioned optimized conditions for S1,decarboxylative borylation of S2a proceeded in lower yield than the NHPIester of S2.

TABLE 8

RAEs Yield* X = H 39% X = Cl 28% *Yields determined by GC-FID withdodecane as internal standard.

In order to identify a more general set of conditions, furtheroptimization efforts were undertaken on the NHPI ester S2.

TABLE 9

Nickel/ligand Yield* NiCl₂•6H₂O/L1 67% (65%^(†)) NiCl₂•6H₂O/L2 28%NiCl₂•6H₂O/L4 32% NiCl₂•6H₂O/L5 55% NiCl₂•glyme/L1 53% NiBr₂•glyme/L164% Ni(OAc)₂•4H₂O/L1 61% Ni(acac)₂/L1 46% Ni(ONO₃)₂•6H₂O/L1 58% *Yieldsdetermined by GC-FID with dodecane as internal standard. ^(†)Isolatedyield.

TABLE 10

Solvent Yield* THF (0.4 mL) 54% DMF (0.4 mL) 44% THF/DMF (0.2/0.2 mL)67% THF/DMF (0.4/0.2 mL) 67% (65%^(†)) THF/DMF (0.6/0.2 mL) 67% THF/DMF(1.0/0.2 mL) 62% THF/DMF (1.4/0.2 mL) 57% dioxane/DMF (0.4/0.2 mL) 41%glyme/DMF (0.4/0.2 mL) 49% diglyme/DMF (0.4/0.2 mL) 43% Et₂O/DMF(0.4/0.2 mL) 38% THF/DMA (0.4/0.2 mL) 39% THF/CH₃CN (0.4/0.2 mL)  8%THF/HMPA (0.4/0.2 mL) 63% THF/DMPU (0.4/0.2 mL) 45% THF/DMSO (0.4/0.2mL) 10% THF/NMP (0.4/0.2 mL) 45% *Yields determined by GC-FID withdodecane as internal standard. ^(†)Isolated yield.

This optimized set of condition for the decarboxylative borylation of S2(1° RAE) was more general, and was also suitable for 2 (20 RAE).

Further screening indicated that employing THF as sole solvent gave thebest yield for tertiary carboxylic acids (3° RAEs).

TABLE 11

X Ligand Solvent Yield* H L2 THF (0.4 mL) 26% H Ll THF (0.4 mL)74%(68%^(†)) H L1 THF/DMF (0.4/0.2 mL) 66% H L5 THF (0.4 mL) 62% Cl L2THF (0.4 mL) 70% Cl L1 THF (0.4 mL) 52% *Yields determined by GC-FIDwith dodecane as internal standard. ^(†)Isolated yield.

General Procedure for Ni-Catalyzed Borylation of Redox-Active Esters

Part I. Preparation of NiCl₂.6H₂O/Ligand Stock Solution or Suspension(1) Suspension A: NiCl₂.6H₂O/Di-MeObipy (L1) in THF (0.025 M).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-dimethoxy-2,2′-bipyridine (L1, 28.1 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. THF (4.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight (or until no granular NiCl₂.6H₂O was observed) to afford apale green suspension.

(2) Suspension B: NiCl₂.6H₂O/Di-MeObipy (L1) in DMF (0.05 M).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-dimethoxy-2,2′-bipyridine (L1, 28.1 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. DMF (2.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight to afford a pale green suspension.

(3) Suspension C: NiCl₂.6H₂O/Di-tBubipy (L2) in THF (0.025 M).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-di-tert-butyl-2,2′-bipyridine (L2, 34.8 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. THF (4.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight (or until no granular NiCl₂.6H₂O was observed) to afford apale green suspension.

(4) Solution D: NiCl₂.6H₂O/Di-tBubipy (L2) in DMF (0.05 M).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-di-tert-butyl-2,2′-bipyridine (L2, 34.8 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. DMF (2.0 mL) wasadded and the resulting mixture was stirred at room temperature for 2 hto afford a green solution.

Note: All the solutions or suspensions kept under argon can be used forseveral days without appreciable deteriorations in reaction yields.Part II. Preparation of [B₂Pin₂Me]Li Suspension

To a solution of B₂pin₂ (168 mg, 0.66 mmol) in THF (0.6 mL) was addedMeLi (0.38 mL, 1.6 M in Et₂O, 0.6 mmol) at 0° C. under argon. Thereaction mixture was warmed to room temperature and stirred for 1 h toafford a suspension (sometimes we also experienced to obtain thiscomplex as a clear solution).

Note: The resulting mixture can be stored with stirring for severalhours without appreciable deterioration.

Part III. Ni-Catalyzed Cross-Coupling Reaction General Procedure B

A screw-capped culture tube charged with the redox-active ester (0.2mmol, 1.0 equiv) and MgBr₂.OEt₂ (77 mg, 0.3 mmol, 1.5 equiv) wasevacuated and backfilled with argon for three times. THF (0.8 mL) wasadded, and the mixture was stirred until no granular MgBr₂.OEt₂ wasobserved (ca. 10 min) before suspension B (0.4 mL, NiCl₂.6H₂O (10 mol%)/di-MeObipy (13 mol %) in DMF), or solution D (0.4 mL, NiCl₂.6H₂O (10mol %)/di-tBubipy (13 mol %) in DMF) was added via a syringe. Theresulting mixture was stirred vigorously until no visible solid wasobserved on the bottom of the reaction vessel (ca. 10 min). This mixturewas cooled to 0° C. before a suspension of [B₂pin₂Me]Li in THF (3 eq,1.1 mL) was added in one portion (note: do not add it dropwise!). Afterstirring for 1 h at 0° C., the reaction was warmed to room temperatureand stirred for another 1 h before quenched with 0.1 N HCl (10 mL). Theresulting mixture was extracted with Et₂O or EtOAc (3 mL×2). Thecombined organic layers were concentrated in vacuo, and the crudeproduct was purified by flash column chromatography. For acid labilesubstrate, the reaction was alternatively quenched with saturatedaqueous NH₄Cl (10 mL).

General Procedure C

A screw-capped culture tube charged with the redox-active ester (0.2mmol, 1.0 equiv) and MgBr₂.OEt₂ (77 mg, 0.3 mmol, 1.5 equiv) wasevacuated and backfilled with argon for three times. Suspension A (0.8mL, NiCl₂.6H₂O (10 mol %)/di-MeObipy (13 mol %) in THF) or C (0.8 mL,NiCl₂.6H₂O (10 mol %)/di-tBubipy (13 mol %) in THF) was added via asyringe. The mixture was stirred vigorously at room temperature until nogranular MgBr₂.OEt₂ was observed (ca. 15 min). This suspension wascooled to 0° C. before a suspension of [B₂pin₂Me]Li was added in oneportion (note: do not add it dropwise!). After stirring for 1 h at 0°C., the reaction was warmed to room temperature and stirred for another1 h. The reaction mixture was diluted with Et₂O (10 mL), filteredthrough a short pad of silica gel and celite (top layer: celite, bottomlayer: silica gel, v/v celite:silica gel=1:1), washed with Et₂O (50 mL).The filtrate was concentrated, and the crude product was purified bycolumn chromatography.

For polar substrates, such as peptides, the reaction was quenched eitherwith 0.1 N HCl (10 mL) or sat. aqueous NH₄Cl (10 mL) followed byextraction with EtOAc (3 mL×2). The combined organic layers were driedover Na₂SO₄, concentrated in vacuo and purified by flash columnchromatography.

General Procedure for Gram-Scale Ni-Catalyzed Borylation of Redox-ActiveEsters (Borylation of Ibuprofen).

The gram-scale procedure was slightly modified from General Procedure C.A flame-dried round bottom fask charged with B₂pin₂ (2.57 g, 10.1 mmol,3.3 equiv) was evacuated and backfilled with argon for three times. THF(9.2 mL) was added, and the clear solution was cooled to 0° C. when MeLi(5.8 mL, 1.6 M in Et₂O, 9.3 mmol, 3.0 equiv) was added dropwise. Thereaction mixture was then warmed to room temperature and stirred for 1h.

The NHPI redox-active ester of ibuprofen S18 (1.08 g, 3.07 mmol) andMgBr₂.OEt₂ (powder, 792 mg, 3.07 mmol, 1.0 equiv) were sequentiallyadded to another flame-dried round-bottom flask. This flask wasevacuated and backfilled with argon for three times and was cooled to 0°C. THF (12 mL) was added, the mixture was sonicated until no granularMgBr₂.OEt₂ was observed. A suspension of NiCl₂.6H₂O (73 mg, 0.31 mmol)and di-MeObipy (L2, 86 mg, 0.40 mmol) in THF (12 mL) was added, and theresulting mixture was sonicated again until there was no visible solidon the bottom of the flask. The mixture was then cooled to 0° C. beforea suspension of [B₂pin₂Me]Li in THF was added in one portion. Afterstirring for 1 h at 0° C., the reaction mixture was warmed to roomtemperature and stirred for another 1 h.

The reaction mixture was then poured into Et₂O (100 mL), and the flaskwas rinsed with additional Et₂O (100 mL). The resulting mixture wasfiltered through a plug of silica gel and celite (top layer: celite,bottom layer: silica gel, v/v celite:silica gel=1:1), the solid residuewas washed with Et₂O (350 mL), and the filtrate was concentrated invacuo. Purification by flash column chromatography (silica gel, hexanesto 1:30 Et₂O:hexanes) afforded product (709 mg, 80%) as a colorless oil.

General Procedure for Ni-Catalyzed Decarboxylative Borylation of AlkylCarboxylic Acids Via In Situ Generated RAEs (General Procedure D)

A screw-capped culture tube with a stir bar was charged with alkylcarboxylic acid (0.2 mmol), N-hydroxyphthalimide ortetrachloro-N-hydroxyphthalimide (0.2 mmol, 1.0 equiv) andN,N′-dicyclohexylcarbodiimide (0.2 mmol, 1.0 equiv). The tube was thenevacuated and backfilled with argon for three times. CH₂Cl₂ (2.0 mL) wasadded and the resulting mixture was stirred at room temperature for 2 hbefore the volatiles were removed in vacuo. MgBr₂. OEt₂ (77 mg, 0.3mmol, 1.5 equiv) was added. The tube was evacuated and backfilled withargon for three times. Suspension A (0.8 mL, NiCl₂.6H₂O (10 mol %)/L1(13 mol %) in THF) or suspension C (0.8 mL, NiCl₂.6H₂O (10 mol %)/L2 (13mol %) was added. The mixture was stirred vigorously at room temperaturefor 15 min (or until no granular MgBr₂.OEt₂ was observed) and wassubsequently cooled to 0° C. before a suspension of [B₂pin₂Me]Li in THF(1.1 mL) was added in one portion (note: do not add it dropwise!). Afterbeing stirred for 1 h, the reaction was warmed to room temperature andstirred for another 1 h. The reaction mixture was then quenched with 0.1N HCl (10 mL) and extracted with Et₂O (5 mL×2). The combined organiclayers were dried over Na₂SO₄, concentrated in vacuo and purified bycolumn chromatography to give the desired product.

Examples of Ni-Catalyzed Decarboxylative Borylation of Alkyl CarboxylicAcids Via In Situ Generated RAEs

This in situ procedure was demonstrated on six alkyl carboxylic acidsfollowing General Procedure D.

General Procedure D is Less Effective for Primary Carboxylic Acids(Typically 20% Yield).

General Procedure for Ni-Catalyzed Borylation of Redox-Active Esterswith 2.5 Mol % NickelPart I. Preparation of NiCl₂.6H₂O/Ligand Stock Solution or Suspension(1) Suspension E: NiCl₂.6H₂O/Di-MeObipy (L1) in THF (6.25 mM).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-dimethoxy-2,2′-bipyridine (L1, 28.1 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. THF (16.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight (or until no granular NiCl₂.6H₂O was observed) to afford apale green suspension.

(2) Solution F: NiCl₂.6H₂O/Di-MeObipy (L1) in DMF (12.5 mM).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-dimethoxy-2,2′-bipyridine (L1, 28.1 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. DMF (8.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight to afford a light green solution.

(3) Suspension G: NiCl₂.6H₂O/Di-tBubipy (L2) in THF (6.25 mM).

A screw-capped culture tube charged with NiCl₂.6H₂O (23.8 mg, 0.1 mmol)and 4,4′-di-tert-butyl-2,2′-bipyridine (L2, 34.8 mg, 0.13 mmol) wasevacuated and backfilled with argon for three times. THF (16.0 mL) wasadded and the resulting mixture was stirred at room temperatureovernight (or until no granular NiCl₂.6H₂O was observed) to afford apale green suspension.

Note: All the solutions or suspensions kept under argon can be used fortwo weeks without appreciable deteriorations in reaction yields.

Part II. Ni-Catalyzed Cross-Coupling Reaction

Borylation of redox-active esters with 2.5 mol % nickel loading followedGeneral Procedure B/C with Suspension E/Solution F/Suspension G.Examples of Ni-Catalyzed Borylation of Redox-Active Esters with 2.5 Mol% Nickel

Standard Reaction conditions: Redox active NHPI ester (1.0 equiv),NiCl₂.6H₂O (2.5 mol %), L1 (3.3 mol %), MgBr₂.OEt₂ (1.5 equiv), B₂pin₂(3.3 equiv), MeLi (3.0 equiv), THF/DMF (2.5:1), 0° C.-RT, 2 h.

Copper-Catalyzed Borylation of Redox-Active Esters

In further embodiments of the invention, the copper-catalyzed borylationof alkyl carboxylic acids to yield alkyl boronic acids, is disclosed andclaimed herein. This invention entails the conversion of carboxylatefunctionalities into the corresponding boronic derivatives viacopper-catalyzed decarboxylative borylation of redox active esters. Invarious embodiments, this transformation enables late-stagemodifications of pharmaceuticals or analogs thereof; it allows theexpedient syntheses of boron-containing bioactive molecules, includingFDA-approved drugs; it allows for the preparations of boron-containingbuilding blocks which have been broadly used in the syntheses ofpharmaceutical ingredients. Compared with other methods, it allowssimple procedure and inexpensive reagents which can be readily adoptedin process chemistry.

Cu(II) salts were screened for borylation catalytic activity comprisingcopper complexed with various ligands, including bipyridyl-type ligandsof formula L (e.g., 4,4′-di-t-Bu-2,2′-bipyridyl, L2, see above), and1,3-dicarbonyl-type ligands that form with a copper ion (Cu(I) orCu(II)) a complex of formula M (e.g., acetonylacetonate, M1).

M1-M7

M1 R_(1A)=R_(2A)=Me, Cu(acac)₂M2 R_(1A)=R_(2A)=tBuM3 R_(1A)=R_(2A)=iPrM4 R_(1A)=R_(2A)=PhM5 R_(1A), R_(2A)=tBu, MeM6 R_(1A)=R_(2A)=CF₃M7 R_(1A), R_(2A)=tBu, CF₃

Table 12, below, shows initial screening results using Cu salts (Cu(I)or Cu(II)) with various bases and ligands in carrying out the borylationreaction of the invention. As can be seen, use of phosphine ligands suchas PPh₃ and PCy₃, even in combination with tBubipy (ligand L2) resultedin zero percent product or low yields, but Cu(I) salts with tBubipy withand without MgBr₂ gave a better result.

Table 13 shows a study of results using varying loads of MgBr₂, andvarious Cu salts. As can be seen, MgBr₂ appears to inhibit the reaction;best results were obtained with tBubipy as ligand, no MgBr₂, and CuCl,CuCl2, CuCl₂.6H₂O, CuI, and Cu(OAc)₂ as copper sources; both Cu(I) andCu(II) states were catalytically active in this system.

Table 14 shows the effect of solvent on the copper-catalyzed borylationreaction using lithium t-butoxide, Cu(OAc)₂ (i.e., a Cu(II) salt) in thepresence of the tBubipy ligand L2. the most effective solvent mixturesseem to be DMF plus an ether, such as dioxane, THF, or glyme, diglyme ordiethyl ether, although DMF mixtures with other solvents such as CH₂Cl₂,EtOAc, or toluene, were also effective. Interestingly, pure DMF gave alower yield.

Table 15 shows significant increases in yield obtained using LiOH andLiOtBu, even in the presence of MgBr₂, with Cu(OAc)₂ as the coppersource and tBubipy L2 as the ligand.

Table 16 shows the effect on yield of solvent using variants of thepreferred dixoxane/DMF solvent system, with the Cu(OAc)₂/tBubipycatalytic complex, in the presence of LiOH/MgBr₂-Et₂O. As a replacementfor dioxane, other ethers and esters seem to be most effective. As areplacement for DMF, other dipolar aprotic solvents were effective, aswere pyridine and acetone.

Table 17 shows the effect on yield of catalysts and copper sources usingCu(OAc)₂ as a copper source in the presence of LiOH and MgBr₂-Et₂O indioxane-DMF solvent system. The effective ligands were much as seenbefore, the bipyridyl ligand L2 being more effective than phosphine typeligands, but interestingly it was noted that adding the 1,3-dicarbonylligand acetonylacetonate (acac) increased the yield when tBubipy L2 wasthe primary ligand for the copper complex.

Tables 18 and 19 show the effect on yield using various 1,3-dicarbonyltype ligands, M1-M7, as defined above, in the dioxane-DMF solvent systemin the presence of LiOH and MgBr₂.Et₂O. Ligand M1, copperacetonylacetonate itself, along with other 1,3-dicarbonyl ligands M2-M7,were broadly effective, while when Cu(acac)₂ was the primary catalyst,the presence of other Cu salts did not bring about large changes in theyields obtained.

Table 20 shows the yields of the copper-catalyzed borylation reactionsin the dioxane-DMF solvent system, in the presence of LiOH and in theabsence of any bipyridyl ligand L2, with various Mg sources and LiOHloadings. It was found that MgCl₂ could be substituted for the moreexpensive MgBr₂ with no loss in yield, while LiOH loadings beyond about15 equivalents did not produce a significant yield increase.

Table 21 shows a final optimization of the reaction using Cu(acac)₂ M1in the presence of LiOH and MgCl₂ in dioxane/DMF, with production costestimate comparisons.

TABLE 12 Copper-catalyzed Borylation of Redox-Active Esters; LigandScreening

Entry Conditions Result (tBuOLi (1.5 eq) as base) 1 CuTc/tBubipy (10/10mol %), THF/NMP  0% 2 CuTc/tBubipy/PPh₃ (10/10/10 mol %), THF/NMP  0% 3CuTc/tBubipy/PCy₃ (10/10/10 mol %), THF/NMP  0% tBuOLi (1.5 eq) as base1 CuI/PPh₃, THF  0% 2 CuI/PPh₃, THF/DMF trace 3 CuI/PPh₃, THF,w/MgBr₂∞Et₂O  0% 4 CuI/PPh₃, THF/DMF, w/MgBr₂∞Et₂O  0% 5 CuI/tBubipy,THF 14% 6 CuI/tBubipy, THF/DMF  4% 7 CuI/tBubipy, THF, w/MgBr₂∞Et₂O 21%8 CuI/tBubipy, THF/DMF, w/MgBr₂∞Et₂O 17%

TABLE 13 Copper-catalyzed Borylation of Redox-Active Esters; Effect ofMrBr₂ Loading and Cu Salt

Entry Conditions Result (w/CuI/tBubipy) 1 MgBr₂∞Et₂O, 0 eq 14% 2MgBr₂•Et₂O, 0.2 eq  6% 3 MgBr₂•Et₂O, 0.5 eq  3% 4 MgBr₂•Et₂O, 1.0 eq  0%5 MgBr₂•Et₂O, 1.5 eq  0% tBubipy as ligand, no MgBr₂•Et₂O 1 CuCl 12% 2CuBr  9% 3 CuCN trace 4 Cu(MeCN)₄PF₆  8% 5 CuCl₂ 11% 6 CuCl₂•2H₂O 19% 7CuBr₂  9% 8 CuF₂  0% 9 CuSO₄•5H₂O trace 10 Cu(OAc)₂ 19% 11 CuI (10 mol%), tBubipy (15 mol %) 16% 12 CuI (10 mol %), tBubipy (20 mol %) 19%

TABLE 14 Copper-catalyzed Borylation of Redox-Active Esters

Entry Conditions Result (Cu(OAc)₂/tBubipy (10/10 mol %)) 1 THF only 11%2 THF/DMA 4/1 10% 3 THF/NMP 4/1 11% 4 THF/NMP 9/1 18% 5 THF/CH₃CN 4/111% 6 dioxane/DMF 4/1 24% 7 glyme/DMF 4/1 20% 8 DMF only  5%Cu(OAc)₂/tBubipy (10/20 mol %) 1 THF/DMF 4/1 22% 2 dioxane/DMF 9/1 25% 3ether/DMF 9/1 19% 4 glyme/DMF 9/1 21% 5 diglyme/DMF 9/1 17% 6 hexane/DMF9/1  9% 7 CH₂Cl₂/DMF 9/1 17% 8 toluene/DMF 9/1 23% 9 EtOAc/DMF 9/1 25%

TABLE 15 Copper-catalyzed Borylation of Redox-Active Esters; LiOH vs.LiOtBu, Second Ligand Effect

Entry Conditions Result (Cu(OAc)₂/tBubipy (10/10 mol %)) 1 tBuOLi (4 eq,batch 1), MgBr₂∞Et₂O (0.8 eq) 40% 2 LiOH (4 eq), MgBr₂∞Et₂O (0 eq) 27% 3LiOH (4 eq), MgBr₂∞Et₂O (0.2 eq) 47% 4 LiOH (4 eq), MgBr₂∞Et₂O (0.5 eq)26% 5 LiOH (4 eq), MgBr₂∞Et₂O (0.8 eq) 25% 6 LiOH∞H₂O (4 eq), MgBr₂∞Et₂O(0 eq) 27% 7 LiOH∞H₂O (4 eq), MgBr₂∞Et₂O (0.1 eq) 43% 8 LiOH∞H₂O (4 eq),MgBr₂∞Et₂O (0.2 eq) 48% 9 LiOH∞H₂O (4 eq), MgBr₂∞Et₂O (0.3 eq) 39%LiOH∞H₂O (4 eq), MgBr₂∞Et₂O (0.2 eq) 1 Cu(OAc)₂/tBubipy/PPh₃ (10/10/10mol %) 35% 2 Cu(OAc)₂/tBubipy/PCy₃ (10/10/10 mol %) 35% 3Cu(OAc)₂/tBubipy/PCy₃∞HBF₄ (10/10/10 mol %) 34% 4 Cu(OAc)₂/tBubipy/dppe(10/10/10 mol %) 19% 5 Cu(OAc)₂/dppe (10/10 mol %) 34% 6 Cu(OAc)₂/dppe(10/15 mol %) 16% 7 Cu(OAc)₂/dppe (10/20 mol %) trace

TABLE 16 Copper-catalyzed Borylation of Redox-Active Esters; SolventEffect

Entry Sol A/DMF (6/1) Result Entry Dioxane/sol B (6/1) Result 1 THF 23%1 DMA 32% 2 Et₂O 26% 2 NMP 22% 3 glyme 12% 3 HMPA  6% 4 TBME 35% 4 DMSO24% 5 CH₂Cl₂ 23% 5 CH₃CN 27% 6 toluene 18% 6 DMPU 10% 7 EtOAc 26% 7pyridine 29% 8 acetone  6% 8 TMEDA  9% 9 DMF  9% 9 acetone 31% 10 CH₃CN 5% 10 Et₃N  7% 11 DMSO 11%

TABLE 17 Copper-catalyzed Borylation of Redox-Active Esters; Catalystsand Copper Sources

Entry Cu(OAc)₂/ligand (10/10 mol %) Result Entry Copper/tBubipy (10/10mol %) Result 1 tBubipy 42% 1 CuOAc    3% 2 PPh₃ 36% 2 CuI   35% 3 PCy₃22% 3 CuCl   39% 4 PnBu₃ 10% 4 CuCl₂•2H₂O   36% 5 P(Nap)₃ 29% 5 Cu(TFA)₂  29% 6 SPhos 23% 6 Cu(OTf)₂   40% 7 dppe 45% 7 Cu(ClO₄)₂•6H₂O   40% 8dppp  9% 8 Cu(acac)₂   41% 9 dppb trace Cu(OAc)₂/tBubipy (10/10 mol %)   10 dppbz trace 1 additive K₂CO₃   28% 11 dppf  0% 2 EtOH   13% 12BINAP  9% 3 TBAB   22% 13 Xantphos 10% 4 TBAF    8% 14 IMes•HCl 20% 5pyridine (2 eq)   26% 15 IPr•HCl  0% 6 DMAP   12% 16 IAd•HCl  8% 7 4-CNpyridine   14% 17 bathocuproine 29% 8 FeBr₂   19% 9 NiBr•3H₂O  <5% 10MnBr₂•4H₂O   27%

TABLE 18 Copper-catalyzed Borylation of Redox-Active Esters;1,3-dicarbonyl ligands

Entry Conditions Result (LiOH•H₂O (4 eq), MgBr₂•Et₂O (0.2 eq)) 1Cu(acac)₂ (10 mol %) 47% 2 3 4 5 6 7 R_(1A) = R_(2A) = tBu (10 mol %)R_(1A) = R_(2A) = Pr (10 mol %) R_(1A) = R_(2A) = Ph (10 mol %) R_(1A),R_(2A) = tBu, Me (10 mol %) R_(1A) = R_(2A) = CF₃ (10 mol %) R_(1A),R_(2A) = tBu, CF₃ (10 mol %)

45% 35% 45% 48% 31% 30% LiOH•H₂O (10 eq), MgBr₂•Et₂O (0.8 eq) 1Cu(OAc)₂/tBubipy (10/10 mol %) 62% 2 Cu(acac)₂ (10 mol %) 51% 3Cu(acac)₂ (20 mol %) 62% 4 Cu(acac)₂ (30 mol %) 63% 5 Cu(acac)₂ (20 mol%), additive H₂O (50 uL, 28 eq) 59% 6 Cu(acac)₂ (20 mol %), additivetBuOLi (2 eq) 60% 7 Cu(acac)₂ (10 mol %), CuI (10 mol %) 66% 8 Cu(acac)₂(10 mol %), CuCl (10 mol %) 59% 9 Cu(acac)₂ (10 mol %), Cu(OAc)₂ (10 mol%) 50% 10  Cu(acac)₂/Cu(ClO₄)₂•6H₂O (10/10/10 mol %) 48% 11 Cu(acac)₂/CuCl/tBubipy (10/10/10 mol %) 59% 12 Cu(acac)₂/Cu(OAc)₂/tBubipy (10/10/10 mol %) 59% tBubipy = compound L2;acac = acetylacetonate

TABLE 19 Copper-catalyzed Borylation of Redox-Active Esters

Entry Conditions Result (LiOH•H₂O (4 eq), MgBr₂•Et₂O (0.2 eq)) 1Cu(acac)₂ (10 mol %) 47% 2 3 4 5 6 7 R_(1A) = R_(2A) = tBu (10 mol %)R_(1A) = R_(2A) = iPr (10 mol %) R_(1A) = R_(2A) = Ph (10 mol %) R_(1A),R_(2A) = tBu, Me (10 mol %) R_(1A) = R_(2A) = CF₃ (10 mol %) R_(1A),R_(2A) = tBu, CF₃ (10 mol %)

45% 35% 45% 48% 31% 30% LiOH•H₂O (10 eq), MgBr₂•Et₂O (0.8 eq) 1Cu(OAc)₂/tBubipy (10/10 mol %) 62% 2 Cu(acac)₂ (10 mol %) 51% 3Cu(acac)₂ (20 mol %) 62% 4 Cu(acac)₂ (30 mol %) 63% 5 Cu(acac)₂ (20 mol%), additive H₂O (50 uL, 28 eq) 59% 6 Cu(acac)₂ (20 mol %), additivetBuOLi (2 eq) 60% 7 Cu(acac)₂ (10 mol %), CuI (10 mol %) 66% 8 Cu(acac)₂(10 mol %), CuCl (10 mol %) 59% 9 Cu(acac)₂ (10 mol %), Cu(OAc)₂ (10 mol%) 50% 10  Cu(acac)₂/Cu(ClO₄)2•6H₂O (10/10/10 mol %) 48% 11 Cu(acac)₂/CuCl/tBubipy (10/10/10 mol %) 59% 12 Cu(acac)₂/Cu(OAc)₂/tBubipy (10/10/10 mol %) 59%

TABLE 20 Copper-catalyzed Borylation of Redox-Active Esters; Mg sourceand LiOH Loading

Entry Conditions Result (LiOH•H₂O (10 eq), Cu(acac)₂ (20 mol %)) 1 MgCl₂61% 2 Mg(OTf)₂ 19% 3 Mg(ClO₄)₂ 12% 4 MgO trace 5 Mg(OAc)₂•4H₂O 24%Cu(acac)₂ (20 mol %), MgBr₂•Et₂O (0.8 eq) 1 15 eq LiOH•H₂O (63 mg) 69% 220 eq LiOH•H₂O (84 mg) 69% 3 30 eq LiOH•H₂O (126 mg) 67%

Entry Conditions Result 1 10 eq LiOH•H₂O (42 mg) 55% 2 15 eq LiOH•H₂O(63 mg) 61%

TABLE 21 Reaction Condition Optimization and Cost Estimate Comparison,Cu-catalyzed versus Ni-catalyzed Borylation

Entry Final conditions w/ MgCl₂ Result 1 MgCl₂ (0.8 eq) 59% 2 MgCl₂ (1.5eq) 61% 3 MgCl₂ (1.5 eq), dioxane/DMF 4/1 64% 4 MgCl₂ (1.5 eq),dioxane/DMF 4/1, PPh₃ (20 mol %) 59% B₂Pin₂ LiOH•H2O Cu(acac)2 Mg sourceTotal Cost (/mol) $ 137 $ 66 $ 13 $ 280 (MgBr₂•Et₂O) $ 496 $ 8 (MgCl₂) $224

52%, Scripps (Ni) 48%, Scripps (Ni) 41%, Aggarwal unknown, Aggarwal 69%,Scripps (Cu) 64%, Scripps (Cu) 55% isolated on gram scale (3.5 mmol) 60%isolated on gram scale (2.5 mmol)

Copper-Catalyzed Borylation Procedure: Optimized

Procedure:

To a 15 mL culture tube equipped with a stir bar were added redox-activeester (0.2 mmol), B₂Pin₂ (76 mg, 1.5 eq), LiOH.H₂O (126 mg, 15 eq),Cu(acac)₂ (10.4 mg, 20 mol %) and MgCl₂ (28.5 mg, 1.5 eq). The tube wasevacuated and backfilled with argon for 3 times. Degassed dioxane/DMF(from Acros extra-dry bottles, 4/1, 1.4 mL) was added and the resultingmixture was stirred under 1000 rpm at RT for 30 min before diluted withEtOAc (7 mL) and washed with saturated NH₄Cl (7 mL). The organic phasewas dried over anhydrous Na₂SO₄, evaporated and purified by silica gelchromatography to give the desired product.

Gram Scale Procedure:

To a 50 mL flask equipped with a stir bar were added redox-active ester(1.2 g, 2.5 mmol), B₂Pin₂ (953 mg, 1.5 eq), LiOH.H₂O (1.58 g, 15 eq),Cu(acac)₂ (130 mg, 20 mol %) and MgCl₂ (356 mg, 1.5 eq). The flask wasevacuated and backfilled with argon for 3 times. The solid in the flaskwas stirred for 2 min before degassed dioxane/DMF (from Acros extra-drybottles, 4/1, 17.5 mL) was added and the resulting mixture was stirredunder 1000 rpm at RT for 30 min before diluted with Et₂O (50 mL) andwashed with saturated NH₄Cl (30 mL) and brine (30 mL) successively. Theorganic phase was collected, dried over anhydrous Na₂SO₄, evaporated andpurified by silica gel chromatography to afford the borylation product(625 mg, 60%).

For the adipic acid substrate, shown above, 69% GC yield was obtained on0.2 mmol scale while 55% isolated yield on 3.5 mmol scale. The graphic,below, shows additional substrates and yields obtained in this reactionsystem.

Arylomycin Sidechain Analog Boronic Acid Experimental:

The starting carboxylic acid (50 mg, 0.044 mmol) and N-hydroxyphalmide(6.0 mg, 0.047 mmol, 1.1 eq) was placed in an oven dried culture tubefixed with a stirbar. This was evacuated and backfilled with argon 3times. To this was added DCM (0.5 mL) via syringe, creating asuspension. While stirring, N,N′-diisopropylcarbodiimide (9.5 μL, 7.7mg, 0.047 mmol, 1.1 eq.) was added via syringe. After consumption ofstarting material as monitored by TLC (˜1 h), the solvent was blown offunder a stream of nitrogen, and placed on high vacuum for 2 hours. Afterthis, Cu(acac)₂ (11.5 mg, 0.044 mmol, 1.0 eq.), B₂pin₂ (83.8 mg, 0.33mmol, 7.5 eq.), LiOH.H₂O (55.4 mg, 1.32 mmol, 30 eq.), and MgCl₂ (31.4mg, 0.33 mmol, 7.5 eq.) were quickly added to the tube and resealed. Itwas evacuated and backfilled with argon 3 times. A 6:1 mixture ofdioxane/DMF (0.5 mL) was added to the reaction tube. The resultingmixture was then stirred vigorously for 45 minutes at room temperature.It was then quenched with 2 mL of saturated aqueous NH₄Cl. This wasextracted three times with EtOAc. The combined organic layers wererinsed with brine and dried over MgSO₄. The solvent was removed underreduced pressure. The crude material was purified by a swift flashchromatography column (SiO₂— 3% DCM in MeOH) to provide 31.2 mgsemi-pure product as an off-white solid (˜50% yield). This material wasdissolved in 0.4 mL of dioxane. To this was added 3 mL of 3M HCl (aq.).The resulting mixture was stirred at room temperature for 24 hours. Thereaction was concentrated on a rotary evaporator. The resulting residuewas dissolved in 3 mL of 1:1 MeCN/H₂O and purified by preparatory HPLC(C₁₈; gradient of H₂O to MeCN each containing 0.1% formic acid)providing 2.1 mg.

Copper-Catalyzed Borylation Examples

Experimental Procedures and Characterization Data for Redox-ActiveEsters Compound 2

1,3-dioxoisoindolin-2-yl 2-methyl-4-phenylbutanoate (2)

On 8.75 mmol scale, General Procedure A was followed with2-methyl-4-phenylbutanoic acid. Purification by flash columnchromatography (silica gel, 1:9 EtOAc:hexanes) furnished 2 (2.31 g,82%).

Physical state: colorless oil;

R_(f)=0.60 (silica gel, 3:7 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.92-7.88 (m, 2H), 7.81-7.78 (m, 2H),7.32-7.29 (m, 2H), 7.27-7.25 (m, 2H), 7.22-7.20 (m, 1H), 2.90-2.74 (m,3H), 2.20-2.14 (m, 1H), 1.96-1.90 (m, 1H), 1.40 (d, J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.7, 162.2, 141.3, 134.9, 129.2, 128.7,128.6, 126.2, 124.1, 36.7, 35.7, 33.1, 17.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₁₈NO₄ [M+H]⁺ 324.1230; found324.1230.

Compound S1

4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl 2-methyl-4-phenylbutanoate(S1)

On 13 mmol scale, General Procedure A was followed with2-methyl-4-phenylbutanoic acid. Purification by flash columnchromatography (silica gel, 1:10 EtOAc:hexanes) furnished a yellowproduct. This compound was then recrystallized from CH₂Cl₂/MeOH to yieldS1 (4.12 g, 69%).

Physical state: white solid;

m.p.=80-81° C.;

R_(f)=0.63 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.32-7.28 (m, 2H), 7.26-7.19 (m, 3H),2.89-2.72 (m, 3H), 2.20-2.13 (m, 1H), 1.95-1.88 (m, 1H), 1.39 (d, J=8.4Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.3, 157.8, 141.1, 141.0, 130.6, 128.6,126.3, 124.9, 36.6, 35.5, 33.1, 17.3 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₁₄Cl₄NO₄ [M+H]⁺ 459.9671; found459.9659.

Compound S3

1,3-dioxoisoindolin-2-yl 3-(2-bromophenyl)propanoate (S3)

On 5.0 mmol scale, General Procedure A was followed with3-(2-bromophenyl) propanoic acid. Purification by flash columnchromatography (silica gel, 1:9 EtOAc:hexanes) furnished S3 (1.63 g,87%).

Physical state: white solid;

m.p.=158-160° C.;

R_(f)=0.36 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.87 (m, 2H), 7.80-7.77 (m, 2H), 7.56(dd, J=1.2 Hz, 7.8 Hz, 1H), 7.34 (dd, J=7.8 Hz, 1.8 Hz, 1H), 7.28 (dt,J=7.8 Hz, 1.2 Hz, 1H), 7.12 (dt, J=7.8 Hz, 1.8 Hz, 1H), 3.21 (t, J=7.2Hz, 2H), 3.02 (t, J=7.2 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 168.8, 162.0, 138.5, 134.9, 133.1, 130.1,129.0, 128.7, 127.9, 124.4, 124.1, 31.2, 31.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₇H₁₃BrNO₄ [M+H]⁺ 374.0022; found374.0022.

Compound S4

1,3-dioxoisoindolin-2-yl 6-bromohexanoate (S4)

On 5.0 mmol scale, General Procedure A was followed with 6-bromohexanoicacid. Purification by flash column chromatography (silica gel, 1:10EtOAc:hexanes) furnished S4 (1.52 g, 89%).

Physical state: white solid;

m.p.=60-62° C.;

R_(f)=0.45 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.89-7.86 (m, 2H), 7.79-7.77 (m, 2H), 3.42(t, J=7.2 Hz, 2H), 2.68 (t, J=7.2 Hz, 2H), 1.94-1.89 (m, 2H), 1.84-1.79(m, 2H), 1.63-1.57 (m, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 169.4, 162.0, 134.9, 129.0, 124.1, 33.3,32.3, 30.9, 27.5, 24.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₄H₁₅BrNO₄ [M+H]⁺ 340.0179; found340.0178.

Compound S5

1-(tert-butyl) 5-(1,3-dioxoisoindolin-2-yl)(((9H-fluoren-9-yl)methoxy)carbonyl)-L glutamate (S5)

On 3.0 mmol scale, General Procedure A was followed withFmoc-Glu-O^(t)Bu. Purification by flash column chromatography (silicagel, 1:3 EtOAc:hexanes) furnished S5 (1.53 g, 89%).

Physical state: white foam;

R_(f)=0.49 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.86 (m, 2H), 7.80-7.76 (m, 4H),7.67-7.61 (m, 2H), 7.42-7.38 (m, 2H), 7.31 (dt, J=7.2 Hz, 1.2 Hz, 2H),5.52 (br d, J=7.8 Hz, 1H), 4.50 (dd, J=10.8 Hz, 7.2 Hz, 1H), 4.39-4.36(m, 2H), 4.23 (t, J=7.2 Hz, 1H), 2.82-2.77 (m, 1H), 2.73-2.67 (m, 1H),2.40-2.34 (m, 1H), 2.15-2.09 (m, 1H), 1.50 (s, 9H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 170.6, 169.1, 162.0, 156.2, 143.9, 141.5,134.9, 129.0, 127.9, 127.2, 125.4, 125.2, 124.2, 120.1, 83.1, 67.2,53.7, 47.4, 28.1, 28.0, 27.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₃₂H₃₀N₂NaO₈ [M+Na]⁺ 593.1894; found593.1895;

[α]D²⁰=+5.4 (c 1.0, CHCl₃).

Compound S6

4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl 2-(4-bromophenyl)acetate(S6)

On 5.0 mmol scale, General Procedure A was followed with2-(4-bromophenyl)acetic acid. After completion of the reaction, reactionmixture was filtered through a short pad of silica gel and washed withEtOAc/hexanes (1:8). The filtrate was concentrated, and S6 was obtainedafter recrystallization with CH₂Cl₂/MeOH (1.52 g, 61%).

Physical state: pale yellow solid;

m.p.=212-213° C.;

R_(f)=0.57 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, DMSO-d₆): δ 7.61-7.59 (m, 2H), 7.37-7.35 (m, 2H), 4.25(s, 2H) ppm;

¹³C NMR (151 MHz, DMSO-d₆): δ 167.7, 157.5, 139.3, 131.7, 131.6, 131.6,129.0, 125.2, 120.9, 35.8 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₇BrCl₄NO₄ [M+H]⁺ 495.8307; found495.8323.

Compound S7

4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl 2-methyl-3-phenylpropanoate(S7)

On 5.0 mmol scale, General Procedure A was followed with2-methyl-3-phenylpropanoic acid. Purification by flash columnchromatography (silica gel, 1:10 EtOAc:hexanes) furnished a yellowproduct which was recrystallized from CH₂Cl₂/MeOH to yield S7 (1.45 g,65%).

Physical state: pale yellow solid;

m.p.=127-128° C.

R_(f)=0.63 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.35-7.32 (m, 2H), 7.28-7.23 (m, 3H), 3.25(dd, J=13.8 Hz, 6.6 Hz, 1H), 3.14-3.08 (m, 1H), 2.82 (dd, J=13.8 Hz, 7.8Hz, 1H), 1.34 (d, J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.9, 157.7, 141.2, 137.8, 130.6, 129.2,128.8, 127.0, 124.9, 39.3, 39.0, 16.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₁₂Cl₄NO₄ [M+H]⁺ 445.9515; found445.9516.

Compound S8

1,3-dioxoisoindolin-2-yl 2-phenylpropanoate (S8)

On 5.0 mmol scale, General Procedure A was followed with2-phenylpropanoic acid. Purification by flash column chromatography(silica gel, 1:10 EtOAc:hexanes) furnished S8 (1.19 g, 81%).

Physical state: colorless oil;

R_(f)=0.21 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.87-7.85 (m, 2H), 7.79-7.76 (m, 2H),7.43-7.39 (m, 4H), 7.34-7.31 (m, 1H), 4.13 (q, J=7.2 Hz, 1H), 1.68 (d,J=7.2 Hz, 3H) pm;

¹³C NMR (151 MHz, CDCl₃): δ 170.9, 162.0, 138.5, 134.9, 129.1, 129.1,127.9, 127.7, 124.1, 43.1, 19.1 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₇H₁₄NO₄ [M+H]⁺ 296.0917; found296.0920.

Compound S9

1,3-dioxoisoindolin-2-yl 2,2-diphenylacetate (S9)

On 1.5 mmol scale, General Procedure A was followed with diphenylaceticacid. Purification by flash column chromatography (silica gel, 1:4EtOAc:hexanes) furnished S9 (0.46 g, 86%).

Physical state: white solid;

m.p.=135-137° C.;

R_(f)=0.33 (silica gel, 1:4 EtOAc:hexanes)

¹H NMR (600 MHz, CDCl₃): δ 7.89-7.86 (m, 2H), 7.80-7.77 (m, 2H),7.42-7.37 (m, 8H), 7.34-7.31 (m, 2H), 5.42 (s, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 169.2, 162.0, 136.9, 134.9, 129.1, 129.0,128.9, 128.0, 124.1, 54.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₂H₁₆NO₄ [M+H]⁺ 358.1074; found358.1078.

Compound S10

1,3-dioxoisoindolin-2-yl-bicyclo[2.2.1]heptane-2-carboxylate (S10)

On 3.0 mmol scale, General Procedure A was followed withbicyclo[2.2.1]heptane-2-carboxylic acid (mixture of endo and exo).Purification by flash column chromatography (silica gel, 1:19 to 1:9EtOAc:hexanes) furnished S10 (0.75 g, 88%) as mixture of exo/endoisomers.

Physical state: white solid;

R_(f)=0.41 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.86 (m, 2H), 7.80-7.77 (m, 2H),3.15-3.11 (m, 0.82H), 2.81 (br s, 0.82H), 2.77 (br d, J=4.2 Hz, 0.18H),2.70 (dd, J=9.6 Hz, 6.0 Hz, 0.18H), 2.38 (br t, J=4.2 Hz, 0.18H),2.35-2.33 (br, m, 0.82H), 2.00-1.96 (m, 0.18H), 1.86-1.81 (m, 0.82H),1.74-1.70 (m, 0.82H), 1.63-1.67 (m, 3.28H), 1.51-1.44 (m, 1.64H),1.38-1.25 (m, 1.26H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ171.5, 162.3, 134.8, 129.2, 124.0, 43.4,41.0, 40.5, 37.0, 32.7, 29.0, 24.9 ppm (major isomer); 172.3, 162.3,134.8, 129.2, 124.0, 43.7, 41.7, 36.7, 36.2, 34.6, 29.5, 28.6 ppm (minorisomer).

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₁₆NO₄ [M+H]⁺ 286.1074; found286.1071.

Compound S11

4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yltrans-2-phenylcyclopropane-1-carboxylate (S11)

On 3.0 mmol scale, General Procedure A was followed withtrans-2-phenylcyclopropane-1-carboxylic acid. Upon complete consumptionof starting material (TLC), the reaction mixture was filtered throughcelite, washed with CH₂Cl₂ (100 mL), and concentrated under reducedpressure. The crude product was purified by crystallization(CH₂Cl₂/MeOH) to furnish S11 (949 mg, 71%).

Physical state: pale yellow needle;

m.p.=203-205° C.;

R_(f)=0.48 ((silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.34-7.31 (m, 2H), 7.28-7.25 (m, 1H),7.18-7.16 (m, 2H), 2.80-2.77 (m, 1H), 2.22-2.19 (m, 1H), 1.84 (dt,J=10.2 Hz, 5.4 Hz, 1H), 1.69-1.66 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 169.4, 157.7, 141.2, 138.3, 130.6, 128.8,127.4, 126.5, 124.8, 28.8, 21.0, 18.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₁₀Cl₄NO₄ [M+H]⁺ 443.9358; found443.9356.

Compound S12

1,3-dioxoisoindolin-2-yl 2,2-dimethyl-3-phenylpropanoate (S12)

On 5.0 mmol scale, General Procedure A was followed with2,2-dimethyl-3-phenylpropanoic acid. Purification by flash columnchromatography (silica gel, 1:10 EtOAc:hexanes) furnished S12 (1.36 g,84%).

Physical state: white solid;

m.p.=70-72° C.;

R_(f)=0.45 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.92-7.88 (m, 2H), 7.81-7.78 (m, 2H),7.36-7.31 (m, 4H), 7.29-7.26 (m, 1H), 3.10 (s, 2H), 1.40 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 173.7, 162.2, 136.5, 134.8, 130.6, 129.1,128.3, 127.0, 124.0, 45.8, 43.3, 25.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₁₈NO₄ [M+H]⁺ 324.1230; found324.1232.

Compound S13

1,3-dioxoisoindolin-2-yl 1-phenylcyclohexane-1-carboxylate (S13)

On 5.0 mmol scale, General Procedure A was followed with2-phenylpropanoic acid. Purification by flash column chromatography(silica gel, 1:9 EtOAc:hexanes) furnished S13 (1.64 g, 81%).

Physical state: white solid;

m.p.=108-109° C.;

R_(f)=0.39 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.87-7.84 (m, 2H), 7.78-7.75 (m, 2H),7.54-7.52 (m, 2H), 7.44-7.41 (m, 2H), 7.34-7.31 (m, 1H), 2.64 (br d,J=13.2 Hz, 2H), 1.89-1.73 (m, 7H), 1.37-1.30 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.8, 162.2, 142.3, 134.8, 129.2, 128.9,127.7, 126.1, 124.0, 51.3, 35.5, 25.6, 23.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₁H₂₀NO₄ [M+H]⁺ 350.1387; found350.1387.

Compound S14

1,3-dioxoisoindolin-2-yl 2-methyl-2-phenylpropanoate (S14)

On 5.0 mmol scale, general procedure A was followed with2-methyl-2-phenylpropanoic acid. Purification by flash columnchromatography (silica gel, 1:8 EtOAc:hexanes) furnished S14 (1.32 g,85%).

Physical state: white solid;

m.p.=73-74° C.;

R_(f)=0.36 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.88-7.85 (m, 2H), 7.79-7.75 (m, 2H),7.51-7.49 (m, 2H), 7.44-7.41 (m, 2H), 7.34-7.31 (m, 1H), 1.79 (s, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 173.4, 162.1, 142.7, 134.8, 129.1, 128.8,127.5, 125.9, 124.0 46.5, 27.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₁₆NO₄ [M+H]⁺ 310.1074; found310.1082.

Compound S15

1,3-dioxoisoindolin-2-yl2-(1-(((tert-butoxycarbonyl)amino)methyl)cyclohexyl) acetate (S15)

On 0.44 mmol scale, General Procedure A was followed with Boc protectedgabapentin. Purification by flash column chromatography (silica gel, 1:5EtOAc:hexanes) furnished S15 (165 mg, 85%).

Physical state: white solid;

m.p.=76-79° C.;

R_(f)=0.32 (silica gel, 1:5 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.87 (m, 2H), 7.82-7.77 (m, 2H), 4.95(br t, J=7.2 Hz, 1H), 3.38 (d, J=6.6 Hz, 2H), 2.63 (s, 2H), 1.65-1.43(m, 10H), 1.44 (s, 9H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 168.3, 162.1, 156.6, 135.0, 129.0, 124.2,79.3, 46.9, 39.1, 37.8, 33.9, 28.5, 26.0, 21.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₂H₂₉N₂O₆ [M+H]⁺ 417.2020; found417.2022.

Compound S16

1,3-dioxoisoindolin-2-yl 2-(4-isobutylphenyl)propanoate (S16)

On 5.0 mmol scale, General Procedure A was followed with ibuprofen.Purification by flash column chromatography (silica gel, 1:9EtOAc:hexanes) furnished S16 (1.48 g, 84%).

Physical state: colorless oil;

R_(f)=0.42 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.87-7.85 (m, 2H), 7.79-7.76 (m, 2H), 7.31(d, J=8.4 Hz, 2H), 7.17 (d, J=8.4 Hz, 2H), 4.10 (q, J=7.2 Hz, 1H), 2.48(d, J=7.2 Hz, 2H), 1.91-1.84 (m, 1H), 1.67 (d, J=7.2 Hz, 3H), 0.91 (d,J=6.6 Hz, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.1, 162.0, 141.4, 135.7, 134.8, 129.8,129.1, 127.4, 124.0, 45.2, 42.7, 30.3, 22.5, 19.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₁H₂₂NO₄ [M+H]⁺ 352.1543; found352.1544.

Compound S17

1,3-dioxoisoindolin-2-yl 5-(2,5-dimethylphenoxy)-2,2-dimethylpentanoate(S17)

On 1.0 mmol scale, General Procedure A was followed with gemfibrozil.Purification by flash column chromatography (silica gel, 1:25EtOAc:hexanes) furnished S17 (0.33 g, 84%).

Physical state: white solid;

m.p.=65-67° C.;

R_(f)=0.50 (silica gel, 1:4 EtOAc:hexanes)

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.87 (m, 2H), 7.80-7.77 (m, 2H), 7.01(d, J=7.8 Hz, 1H), 6.67 (d, J=7.8 Hz, 1H), 6.66 (s, 1H), 4.02 (t, J=6.0Hz, 2H), 2.32 (s, 3H), 2.20 (s, 3H), 1.95-2.00 (m, 4H), 1.46 (s, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 173.9, 162.2, 157.1, 136.6, 134.8, 130.4,129.2, 124.0, 123.8, 120.8, 112.1, 67.9, 42.1, 37.5, 31.7, 25.3, 25.1,21.5, 15.9 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₃H₂₆NO₅ [M+H]⁺ 396.1805; found396.1803.

Compound S18

1,3-dioxoisoindolin-2-yl 2-(6-methoxynaphthalen-2-yl)propanoate (S18)

On 5.0 mmol scale, General Procedure A was followed with naproxen.Purification by flash column chromatography (silica gel, 1:7EtOAc:hexanes) furnished S18 (1.65 g, 88%).

Physical state: white solid;

m.p.=110-111° C.;

R_(f)=0.53 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.86 (br s, 2H), 7.80-7.75 (m, 5H), 7.49 (dd,J=8.4 Hz, 1.8 Hz, 1H), 7.17 (dd, J=8.4 Hz, 2.4 Hz, 1H), 7.14 (d, J=2.4Hz, 1H), 4.26 (q, J=7.2 Hz, 1H), 3.92 (s, 3H), 1.75 (d, J=7.2 Hz, 3H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.1, 162.0, 158.0, 134.9, 134.1, 133.6,129.6, 129.1, 127.7, 126.5, 126.0, 124.1, 119.3, 105.8, 55.5, 43.1, 19.2ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₂H₁₈NO₅ [M+H]⁺ 376.1179; found376.1183.

Compound S19

bis(1,3-dioxoisoindolin-2-yl) nonanedioate (S19)

On 5.0 mmol scale, General Procedure A was followed with azelaic acid(5.0 mmol, 1.0 equiv), NHPI (10 mmol, 2.0 equiv), DIC (11 mmol, 2.2equiv) and DMAP (1 mmol, 0.2 equiv). Purification by flash columnchromatography (silica gel, 1:10 EtOAc:CH₂Cl₂) furnished S19 (1.52 g,64%).

Physical state: white solid;

m.p.=103-105° C.;

R_(f)=0.55 (silica gel, 1:1 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.87 (m, 4H), 7.81-7.78 (m, 4H), 2.69(t, J=4.8 Hz, 4H), 1.85-1.80 (m, 4H), 1.53-1.48 (m, 4H), 1.45-1.42 (m,2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 169.1, 161.5, 134.3, 128.5, 123.5, 30.5,28.1, 28.0, 24.1 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₅H₂₃N₂O₈ [M+H]⁺ 479.1449; found479.1451.

Compound S20

1,3-dioxoisoindolin-2-yl 4-(4-(bis(2-chloroethyl)amino)phenyl)butanoate(S20)

On 1.0 mmol scale, General Procedure A was followed with chlorambucil.Purification by flash column chromatography (silica gel, 1:4EtOAc:hexanes) furnished S20 (431 mg, 96%).

Physical state: yellow oil;

R_(f)=0.23 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.91-7.87 (m, 2H), 7.81-7.77 (m, 2H), 7.12(d, J=8.5 Hz, 2H), 6.65 (d, J=9.0 Hz, 2H), 3.66 (AB t, J=6.7 Hz, 4H),3.63 (BA t, J=6.7 Hz, 4H), 2.67 (dt, J=7.5 Hz, 16 Hz, 4H), 2.09-2.02 (m,2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 169.6, 162.1, 144.7, 134.9, 130.0, 129.1,124.1, 112.4, 53.8, 40.7, 33.6, 30.3, 26.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₂H₂₃Cl₂N₂O₄ [M+H]⁺ 449.1029; found449.1009.

Compound S21

1,3-dioxoisoindolin-2-yl 2-(3-benzoylphenyl)propanoate (S21)

On 5.0 mmol scale, General Procedure A was followed with ketoprofen.Purification by flash column chromatography (silica gel, 1:3EtOAc:hexanes) furnished S21 (1.91 g, 96%).

Physical state: white solid;

m.p.=118-120° C.;

R_(f)=0.45 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.88-7.84 (m, 5H), 7.80-7.76 (m, 3H), 7.67(dt, J=8.4 Hz, 1.2 Hz, 1H), 7.61-7.58 (m, 1H), 7.55-7.48 (m, 3H), 4.20(q, J=7.2 Hz, 1H), 1.71 (d, J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 196.4, 170.6, 161.9, 138.7, 138.4, 137.5,134.9, 132.7, 131.7, 130.3, 129.8, 129.5, 129.1, 129.1, 128.5, 124.1,43.0, 19.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₄H₁₈NO₅ [M+H]⁺ 400.1179; found400.1181.

Compound S22

1,3-dioxoisoindolin-2-yl 2-(3-phenoxyphenyl)propanoate (S22)

On 5.0 mmol scale, General Procedure A was followed with fenoprofen.Purification by flash column chromatography (silica gel, 1:8EtOAc:hexanes) furnished S22 (1.83 g, 94%).

Physical state: colorless oil;

R_(f)=0.50 (silica gel, 1:4 EtOAc:hexanes)

¹H NMR (600 MHz, CDCl₃): δ 7.89-7.85 (m, 2H), 7.79-7.76 (m, 2H),7.37-7.33 (m, 3H), 7.16 (dt, J=7.8 Hz, 1.2 Hz, 1H), 7.13-7.10 (m, 1H),7.09 (t, J=2.4 Hz, 1H), 7.07-7.04 (m, 2H), 6.95 (ddd, J=7.8 Hz, 2.4 Hz,0.6 Hz, 1H), 4.09 (q, J=7.2 Hz, 1H). 1.67 (d, J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 170.6, 161.9, 157.8, 157.1, 140.3, 134.9,130.3, 129.9, 129.1, 124.1, 123.5, 122.5, 119.2, 118.4, 118.2, 42.9,19.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₃H₁₈NO₅[M+H]⁺ 388.1179; found 388.1178.

Compound S23

1,3-dioxoisoindolin-2-yl2-((4R,6R)-6-(2-(2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-(phenylcarbamoyl)-1H-pyrrol-1-yl)ethyl)-2,2-dimethyl-1,3-dioxan-4-yl)acetate(S23)

On 0.5 mmol scale, General Procedure A was followed with ketal ester ofatorvastatin. Purification by flash column chromatography (silica gel,1:2 EtOAc:hexanes) furnished S23 (0.35 g, 95%).

Physical state: yellow foam;

R_(f)=0.35 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.87 (m, 2H), 7.81-7.77 (m, 2H),7.21-7.15 (m, 9H), 7.08 (d, J=8.4 Hz, 2H), 7.02-6.97 (m, 3H), 6.88 (brs, 1H), 4.33-4.28 (m, 1H), 4.14-4.07 (m, 1H), 3.89-3.84 (m, 1H),3.75-3.71 (m, 1H), 3.61-3.56 (m, 1H), 2.85 (dd, J=15.6 Hz, 6.6 Hz, 1H),2.69 (dd, J=15.0 Hz, 6.6 Hz, 1H), 1.76-1.70 (m, 2H), 1.55-1.53 (m, 7H),1.40 (s, 3H), 1.35 (s, 3H), 1.18 (dd, J=12.0 Hz, 5.4 Hz, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 166.9, 164.9, 162.4 (d, J=247.8 Hz), 161.9,141.6, 138.5, 134.9, 134.8, 133.3 (d, J=8.0 Hz), 130.6, 129.0, 128.9,128.8, 128.4, 128.3 (d, J=3.6 Hz), 126.7, 124.1, 123.6, 121.9, 119.7,115.5 (d, J=21.3 Hz), 99.2, 66.4, 65.6, 40.9, 38.4, 38.1, 35.8, 29.9,26.2, 21.9, 21.7, 19.7 ppm;

¹⁹F NMR (376 MHz, CDCl₃): δ −113.91 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₄₄H₄₃FN₃O₇[M+H]⁺ 744.3080; found744.3061.

[α]D²⁰=+25.1 (c 1.0, CHCl₃).

Compound S24

1,3-dioxoisoindolin-2-yl(2S,4aS,6aS,6bR,8aR,10S,12aS,12bR,14bR)-10-acetoxy-2,4a,6a,6b,9,9,12a-heptamethyl-13-oxo-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,13,14b-icosahydropicene-2-carboxylate(S24)

On 1.0 mmol scale, General Procedure A was followed with acetylenoxolone. Purification by flash column chromatography (silica gel, 1:5EtOAc:hexanes) afforded S24 (0.49 g, 75%).

Physical State: white solid;

m.p.=264° C.;

R_(f)=0.57 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.89-7.86 (m, 2H), 7.80-7.77 (m, 2H), 5.76(s, 1H), 4.51 (dd, J=11.8, 4.6 Hz, 1H), 2.79 (dt, J=13.7, 3.7 Hz, 1H),2.45 (ddd, J=13.7, 4.3, 1.7 Hz, 1H), 2.35 (s, 1H), 2.15-2.11 (m, 1H),2.11-2.00 (m, 2H), 2.04 (s, 3H), 1.86 (td, J=13.7, 4.7 Hz, 1H), 1.79 (t,J=13.7 Hz, 1H), 1.74-1.55 (m, 4H), 1.51-1.40 (m, 4H), 1.43 (s, 3H), 1.37(s, 3H), 1.20 (ddd, J=13.8, 4.6, 2.4 Hz, 1H), 1.15 (s, 3H), 1.14 (s,3H), 1.10-1.01 (m, 3H), 0.90 (s, 3H), 0.87 (s, 6H), 0.80 (dd, J=11.9,1.8 Hz, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 200.0, 172.7, 171.1, 168.5, 162.2, 134.8,129.2, 129.0, 124.0, 80.8, 61.9, 55.2, 47.9, 45.5, 44.0, 43.3, 41.3,38.9, 38.2, 37.4, 37.1, 32.9, 32.0, 31.6, 28.5, 28.2, 28.1, 26.6, 26.6,23.7, 23.4, 21.5, 18.8, 17.5, 16.8, 16.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₄₀H₅₂NO₇ [M+H]⁺ 658.3738; found658.3736;

[α]D²⁰=+191.0 (c 1.0, CHCl₃).

Compound S25

1,3-dioxoisoindolin-2-yl(E)-6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydroisobenzofuran-5-yl)-4-methylhex-4-enoate(S25)

On 1.0 mmol scale, General Procedure A was followed with mycophenolicacid. Purification by flash column chromatography (silica gel, 1:4EtOAc:hexanes) furnished S25 (0.36 g, 78%).

Physical state: white solid;

m.p.=126-128° C.;

R_(f)=0.40 (silica gel, 1:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.88-7.85 (m, 2H), 7.79-7.77 (m, 2H), 7.68(s, 1H), 5.34 (t, J=7.2 Hz, 1H), 5.19 (s, 2H), 3.77 (s, 3H), 3.42 (d,J=6.6 Hz, 2H), 2.76 (t, J=7.8 Hz, 2H), 2.45 (t, J=7.8 Hz, 2H), 2.15 (s,3H), 1.85 (s, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 173.0, 169.3, 163.8, 162.0, 153.8, 144.2,134.9, 133.1, 129.0, 124.1, 123.9, 122.0, 116.8, 106.5, 70.2, 61.2,34.1, 29.9, 22.8, 16.2, 11.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₅H₂₄NO₈ [M+H]⁺ 466.1496; found466.1499.

The preparation and spectral data of the following RAEs have beenreported.^(i 22-26)

Experimental Procedure and Characterization Data for Borylation ProductsCompound 3

4,4,5,5-tetramethyl-2-(4-phenylbutan-2-yl)-1,3,2-dioxaborolane (3)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester (2)and suspension B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification by flashcolumn chromatography (silica gel, hexanes to 1:35 Et₂O:hexanes)afforded 3 (32.7 mg, 63%).

Physical state: colorless oil;

R_(f)=0.49 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.28-7.25 (m, 2H), 7.20-7.14 (m, 3H),2.66-2.58 (m, 2H), 1.82-1.76 (m, 1H), 1.62-1.57 (m, 1H), 1.25 (s, 12H),1.10-1.05 (m, 1H), 1.02 (d, J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 143.2, 128.6, 128.3, 125.6, 83.0, 35.5,35.4, 25.0, 24.9, 15.7 ppm;

Spectroscopic data matches that reported in the literature.²

Compound 4

4,4,5,5-tetramethyl-2-(4-phenylbutyl)-1,3,2-dioxaborolane (4)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester (S2)and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification by flashcolumn chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 4 (34.0 mg, 65%).

Physical state: colorless oil;

R_(f)=0.50 (silica gel, 1:12 EtOAc:Hexane);

¹H NMR (600 MHz, CDCl₃): δ 7.28-7.25 (m, 2H), 7.18-7.15 (m, 3H), 2.61(t, J=7.8 Hz, 2H), 1.66-1.61 (m, 2H), 1.50-1.45 (m, 2H), 1.24 (s, 12H),0.82 (t, J=7.8 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 143.1, 128.5, 128.3, 125.6, 83.0, 35.9,34.3, 25.0, 23.9 ppm;

Spectroscopic data matches that reported in the literature.³

Compound 5

Methyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pentanoate (5)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S26) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:100CH₂Cl₂:hexanes) afforded 5 (25.2 mg, 52%).

Physical state: colorless oil;

R_(f)=0.55 (silica gel, 1:6 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 3.64 (s, 3H), 2.29 (t, J=7.2 Hz, 2H),1.64-1.59 (m, 2H), 1.45-1.40 (m, 2H), 1.23 (s, 12H), 0.78 (t, J=7.8 Hz,2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 174.4, 83.1, 51.6, 34.1, 27.7, 25.0, 23.8ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₂H₂₄BO₄ [M+H]⁺ 243.1762; found243.1765.

Compound 6

2-(2-bromophenethyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (6)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester (S3)and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification by flashcolumn chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 6 (34.3 mg, 55%).

Physical state: colorless oil;

R_(f)=0.55 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.50 (d, J=7.8 Hz, 1H), 7.27 (d, J=7.8 Hz,1H), 7.21 (t, J=7.8 Hz, 1H), 7.02 (t, J=7.8 Hz, 1H), 2.84 (t, J=7.8 Hz,2H), 1.24 (s, 12H), 1.15 (t, J=7.8 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 143.7, 132.8, 129.9, 127.4, 127.4, 124.5,83.32, 30.6, 25.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₄H₂₁BBrO₂ [M+H]⁺ 313.0798; found313.0799.

Compound 7

2-(5-bromopentyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester (S4)and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification by flashcolumn chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 7 (36.0 mg, 65%).

Physical state: colorless oil;

R_(f)=0.55 (silica gel, 1:12 EtOAc:hexanes)

¹H NMR (600 MHz, CDCl₃): δ 3.40 (t, J=7.2 Hz, 2H), 1.88-1.83 (m, 2H),1.45-1.42 (m, 4H), 1.24 (s, 12H), 0.80-0.77 (m, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 83.1, 34.2, 32.8, 31.0, 25.0, 23.4 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₁H₂₃BBrO₂ [M+H]⁺ 277.0969; found277.0968.

Compound 8

tert-butyl2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)butanoate(8)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester (S5)and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification by flashcolumn chromatography (silica gel, 1:12 EtOAc:hexanes to 1:6EtOAc:hexanes to 1:4 EtOAc:hexanes) afforded 8 (37.6 mg, 37%).

Physical state: colorless oil;

R_(f)=0.40 (silica gel, 1:4 EtOAc:hexanes)

¹H NMR (600 MHz, CDCl₃): δ 7.76 (d, J=7.2 Hz, 2H), 7.61 (d, J=7.2 Hz,2H), 7.41-7.38 (m, 2H), 7.33-7.30 (m, 2H), 5.53 (d, J=8.4 Hz, 1H),4.34-4.24 (m, 2H), 4.23-4.19 (m, 2H), 1.97-1.91 (m, 1H), 1.84-1.78 (m,1H), 1.47 (s, 9H), 1.23 (s, 12H), 0.89-0.78 (m, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.8, 156.2, 144.2, 144.1, 141.4, 127.8,127.2, 125.3, 120.1, 83.5, 81.9, 67.0, 56.1, 47.4, 28.2, 27.0, 25.0,24.9 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₉H₃₈BNNaO₆ [M+Na]⁺ 530.2684; found530.2685;

[α]D²⁰=+2.3 (c 0.35, CHCl₃).

Compound 9

2-(4-bromobenzyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (9)

On 0.2 mmol scale, General Procedure C was followed with TCNHPI ester(S6) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, 1:40 to 1:20 Et₂O:hexanes)afforded 9 (30.5 mg, 51%).

Physical State: colorless oil;

R_(f)=0.30 (silica gel, 1:19 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.35-7.33 (m, 2H), 7.06-7.04 (m, 2H), 2.23(s, 2H), 1.23 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 137.8, 131.4, 130.9, 118.7, 83.7, 24.9 ppm;

Spectroscopic data matches that reported in the literature.⁴

Compound 10

4,4,5,5-tetramethyl-2-(1-phenylpropan-2-yl)-1,3,2-dioxaborolane (10)

On 0.2 mmol scale, General Procedure C was followed with TCNHPI ester(S7) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:35 Et₂O:hexanes)afforded 10 (33.1 mg, 67%).

Physical state: colorless oil;

R_(f)=0.53 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.26-7.13 (m, 5H), 2.81 (dd, J=13.8 Hz, 7.8Hz, 1H), 2.54 (dd, J=13.8 Hz, 7.8 Hz, 1H), 1.41-1.34 (m, 1H), 1.19 (s,6H), 1.18 (s, 6H), 0.97 (d, J=7.8 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 142.5, 129.0, 128.1, 125.7, 83.1, 39.1,24.9, 15.3 ppm;

Spectroscopic data matches that reported in the literature.⁵

Compound 11

4,4,5,5-tetramethyl-2-(1-phenylethyl)-1,3,2-dioxaborolane (11)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S8), MgBr₂.OEt₂ (52 mg, 0.2 mmol, 1 equiv) and suspension A(NiCl₂.6H₂O/di-MeObipy in THF). Purification by flash columnchromatography (silica gel, hexanes to 1:30 Et₂O:hexanes) afforded 11(33.8 mg, 73%).

Physical State: colorless oil;

R_(f)=0.33 (silica gel, 1:19 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.27-7.21 (m, 4H), 7.15-7.12 (m, 1H), 2.44(q, J=7.8 Hz, 1H), 1.33 (d, J=7.8 Hz, 3H), 1.21 (s, 6H), 1.20 (s, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 145.1, 128.4, 127.9, 125.2, 83.4, 24.8,24.7, 17.2 ppm;

Spectroscopic data matches that reported in the literature.²

Compound 12

2-benzhydryl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (12)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester (S9)and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification by flashcolumn chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 12 (41.0 mg, 69%).

Physical State: colorless oil;

R_(f)=0.41 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.30-7.25 (m, 8H), 7.19-7.15 (m, 2H), 3.88(s, 1H), 1.24 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 142.2, 129.2, 128.5, 125.7, 83.9, 24.7 ppm;

Spectroscopic data matches that reported in the literature.⁶

Compound 13

2-(4,4-difluorocyclohexyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (13)

On 0.2 mmol scale, General Procedure C was followed with TCNHPI ester(S27) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:45 Et₂O:hexanes)afforded 13 (23.0 mg, 47%).

Physical state: colorless oil;

R_(f)=0.45 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 2.02-1.95 (m, 2H), 1.82-1.78 (m, 2H),1.75-1.58 (m, 4H), 1.23 (s, 12H), 1.00-0.96 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 123.9 (t, J=239.9 Hz), 83.4, 34.5 (t, J=23.3Hz), 24.9, 24.4 (t, J=4.6 Hz) ppm;

HRMS (ESI-TOF, m/z): High-resolution mass spec data could not beobtained for this compound.

Compound 14

2-(heptan-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (14)

On 0.2 mmol scale, General Procedure C was followed with TCNHPI ester(S26) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:40 Et₂O:hexanes)afforded 14 (25.6 mg, 57%).

Physical state: colorless oil;

R_(f)=0.42 (silica gel, 1:19 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 1.45-1.22 (m, 20H), 0.90-0.86 (m, 7H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 82.9, 31.7, 30.8, 25.0, 24.4, 23.1, 14.3,13.9 ppm;

Spectroscopic data matches that reported in the literature.

Compound 15

tert-butyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyrrolidine-1-carboxylate(15)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S29) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (first flash column chromatography:deactivate silica gel, hexanes to 1:9 EtOAc:hexanes; second flash columnchromatography (deactivated silica gel, CH₂Cl₂) afforded 15 (39.2 mg,66%).

Physical State: colorless oil;

R_(f)=0.45 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 3.42-2.99 (m, 3H), 2.09-1.65 (m, 4H), 1.43(s, 9H), 1.26-1.22 (m, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 155.1, 83.6, 79.1, 46.1, 28.7, 27.9, 27.325.2, 25.0, 24.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₅H₂₉BNO₄ [M+H]⁺ 298.2184; found298.2179;

[α]D²⁰=0 (c 0.3, CHCl₃).

Compound 16

2-(bicyclo[2.2.1]heptan-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(16)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S10) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:40 Et₂O:hexanes to1:20 Et₂O:hexanes) afforded 16 (24.4 mg, 55%) as mixture of exo/endoisomers.

Physical state: colorless oil;

R_(f)=0.38 (silica gel, 1:19 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 2.28-2.27 (m, 1H), 2.22-2.21 (m, 1H),1.56-1.44 (m, 3H), 1.37-1.33 (m, 1H), 1.26-1.21 (m, 14H), 1.20-1.14 (m,2H), 0.89-0.86 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 82.9, 38.9, 38.3, 36.8, 32.4, 32.3, 29.4,24.9 ppm (exo); 83.0, 41.1, 39.1, 37.2, 32.3, 30.0, 28.0, 25.1, 25.0 ppm(endo);

Spectroscopic data matches that reported in the literature.⁸

Compound 17

2-adamantan-2-yl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (17)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S28) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 17 (30.9 mg, 59%).

Physical state: colorless oil;

R_(f)=0.55 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 2.06-2.04 (m, 2H), 1.90-1.67 (m, 12H),1.37-1.35 (m, 1H), 1.25 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 82.9, 39.5, 37.9, 36.4, 29.5, 28.4, 28.3,25.0 ppm;

Spectroscopic data matches that reported in the literature.²

Compound 18

trans-4,4,5,5-tetramethyl-2-(2-phenylcyclopropyl)-1,3,2-dioxaborolane(18)

On 0.2 mmol scale, General Procedure B was followed with TCNHPI ester(S11) and solution D (NiCl₂.6H₂O/di-tBubipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 18 (11.3 mg, 23%, dr>20:1).

Physical State: colorless oil;

R_(f)=0.48 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.25-7.22 (m, 2H), 7.15-7.11 (m, 1H),7.09-7.06 (m, 2H), 2.10 (dt, J=7.8 Hz, 5.4 Hz, 1H), 1.25 (s, 6H), 1.24(s, 6H), 1.17-1.14 (m, 1H), 1.02-0.99 (m, 1H), 0.32-0.29 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 143.5, 128.4, 125.8, 125.7, 83.3, 24.9,24.8, 22.0, 15.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₅H₂₂BO₂ [M+H]⁺ 245.1707; found245.1714.

Compound 19

4,4,5,5-tetramethyl-2-(2-methyl-1-phenylpropan-2-yl)-1,3,2-dioxaborolane(19)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S12) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 19 (35.3 mg, 68%).

Physical State: colorless solid;

-   -   m.p.=36-37° C.;

R_(f)=0.50 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.24-7.19 (m, 4H), 7.17-7.14 (m, 1H), 2.61(s, 2H), 1.21 (s, 12H), 0.94 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 140.6, 130.3, 127.8, 125.8, 83.24, 46.5,24.9 ppm.

Spectroscopic data matches that reported in the literature.²

Compound 20

2-adamantan-1-yl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (20)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S31) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, 1:60 Et₂O:hexanes to 1:40Et₂O:hexanes) afforded 20 (29.2 mg, 56%).

Physical State: white amorphous solid;

R_(f)=0.60 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 1.84 (br s, 3H), 1.75 (br t, J=3.6 Hz, 12H),1.20 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 82.7, 38.1, 37.6, 27.7, 24.8 ppm;

Spectroscopic data matches that reported in the literature.²

Compound 21

methyl4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)cubane-1-carboxylate (21)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S32) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:15:15Et₂O:CH₂Cl₂:hexanes) afforded 21 (26.2 mg, 46%).

Physical State: white solid;

m.p.=152-155° C.;

R_(f)=0.45 (silica gel, 1:6 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 4.30-4.28 (m, 3H), 4.03-4.01 (m, 3H), 3.70(s, 3H), 1.26 (s, 12H);

¹³C NMR (151 MHz, CDCl₃): δ 172.8, 83.4, 55.4, 51.6, 47.0, 45.2, 24.9ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₂₂BO₄ [M+H]⁺ 289.1606; found289.1607.

Compound 22

Methyl4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)bicyclo[2.2.2]octane-1-carboxylate(22)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S34) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:9 Et₂O:hexanes)afforded 22 (31.1 mg, 53%).

Physical State: colorless solid; Sublimation at 100° C.;

R_(f)=0.39 (silica gel, 1:5 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 3.62 (s, 3H), 1.72-1.65 (m, 6H), 1.62-1.54(m, 6H), 1.19 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 179.0, 83.0, 51.7, 38.6, 27.9, 26.7, 24.8ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₂₈BO₄ [M+H]⁺ 295.2075; found295.2077.

Compound 23

4,4,5,5-tetramethyl-2-(1-methylcyclohexyl)-1,3,2-dioxaborolane (23)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S33) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 23 (27.8 mg, 62%).

Physical State: colorless oil;

R_(f)=0.50 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 1.84-1.80 (m, 2H), 1.64-1.57 (m, 3H),1.29-1.21 (m, 14H), 1.16-1.08 (m, 1H), 0.92-0.87 (m, 5H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 82.9, 37.2, 26.6, 26.0, 25.7, 24.8 ppm;

Spectroscopic data matches that reported in the literature.²

Compound 24

4,4,5,5-tetramethyl-2-(1-phenylcyclohexyl)-1,3,2-dioxaborolane (24)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S13) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 24 (28.5 mg, 50%).

Physical State: white solid;

m.p.=87-88° C.;

R_(f)=0.60 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.36-7.34 (m, 2H), 7.29-7.26 (m, 2H),7.13-7.11 (m, 1H), 2.36-2.32 (m, 2H), 1.82-1.78 (m, 2H), 1.70-1.66 (m,1H), 1.49-1.38 (m, 4H), 1.21-1.14 (m, 1H), 1.17 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 147.6, 128.2, 126.3, 125.1, 83.4, 35.0,26.4, 25.9, 25.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₂₈BO₂ [M+H]⁺ 287.2177; found287.2184.

Compound 25

tert-butyldimethyl(2-methyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propoxy)silane(25)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S30) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 25 (41.2 mg, 66%).

Physical State: colorless oil;

R_(f)=0.40 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 3.39 (s, 2H), 1.22 (s, 12H), 0.90 (s, 6H),0.88 (s, 9H), 0.01 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 83.0, 72.0, 26.1, 24.9, 21.4, 18.5, −5.34ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₃₆BO₃Si [M+H]⁺ 315.2521; found315.2523.

Compound 26

4,4,5,5-tetramethyl-2-(2-phenylpropan-2-yl)-1,3,2-dioxaborolane (26)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S14) and suspension C (NiCl₂.6H₂O/di-tBubipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 26 (23.3 mg, 47%).

Physical State: colorless oil;

R_(f)=0.51 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.33-7.27 (m, 4H), 7.15-7.12 (m, 1H), 1.35(s, 6H), 1.20 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 148.8, 128.2, 126.4, 125.1, 83.4, 25.7, 24.7ppm;

Spectroscopic data matches that reported in the literature.⁹

Compound 27

2-(1-(4-chlorophenyl)cyclopropyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(27)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S34) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 27 (32.9 mg, 59%).

Physical State: White solid;

-   -   m.p.=83-85° C.;

R_(f)=0.37 (silica gel, 1:19 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.19 (s, 4H), 1.21 (s, 12H), 1.11 (dd, J=6.0Hz, 3.6 Hz, 2H), 0.87 (dd, J=6.0 Hz, 3.6 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 143.5, 131.0, 130.5, 128.2, 83.6, 24.7, 13.6ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₅H₂₁BClO₂ [M+H]⁺ 279.1318; found279.1319.

Compound 28

tert-butyl((1-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)methyl)cyclohexyl)methyl)carbamate (28)

On 0.1 mmol scale, General Procedure B was followed with NHPI ester(S15) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, 1:20 EtOAc:hexanes) afforded 28(22.5 mg, 64%).

Physical State: white solid;

m.p.=92-96° C.;

R_(f)=0.28 (silica gel, 1:20 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 5.32 (br s, 1H), 3.08 (d, J=6.0 Hz, 2H),1.52-1.41 (m, 4H), 1.43 (s, 9H), 1.38-1.31 (m, 6H), 1.25 (s, 12H), 0.81(s, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 156.5, 83.4, 78.7, 50.0, 36.7, 36.3, 28.6,26.4, 25.0, 21.9 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₃₇BNO₄ [M+H]⁺ 354.2810; found354.2809.

Compound 29

2-(1-(4-isobutylphenyl)ethyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(29)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S16), MgBr₂.OEt₂ (52 mg, 0.2 mmol, 1 equiv) and suspension A(NiCl₂.6H₂O/di-MeObipy in THF). Purification by flash columnchromatography (silica gel, hexanes to 1:30 Et₂O:hexanes) afforded 29(43.0 mg, 75%).

Physical State: colorless oil;

R_(f)=0.59 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.12-7.10 (m, 2H), 7.04-7.02 (m, 2H), 2.42(d, J=7.2 Hz, 2H), 2.40 (q, J=7.2 Hz, 1H), 1.79-1.88 (m, 1H), 1.31 (d,J=7.2 Hz, 3H), 1.21 (s, 6H), 1.20 (s, 6H), 0.89 (d, J=6.6 Hz, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 142.1, 138.4, 129.2, 127.6, 83.4, 45.2,30.4, 24.8, 24.7, 22.6, 17.2 ppm;

Spectroscopic data matches that reported in the literature.¹⁰

Compound 30

2-(5-(2,5-dimethylphenoxy)-2-methylpentan-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(30)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S17) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:30 Et₂O:hexanes)afforded 30 (36.3 mg, 55%).

Physical State: colorless solid;

m.p.=59-61° C.;

R_(f)=0.60 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 6.99 (d, J=7.8 Hz, 1H), 6.64 (d, J=7.2 Hz,1H), 6.62 (s, 1H), 3.92 (t, J=6.6 Hz, 2H), 2.30 (s, 3H), 2.18 (s, 3H),1.78-1.73 (m, 2H), 1.41-1.44 (m, 2H), 1.23 (s, 12H), 0.96 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 157.3, 136.5, 130.4, 123.8, 120.6, 112.2,83.1, 68.8, 37.4, 26.6, 25.0, 24.9, 21.6, 16.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₀H₃₄BO₃ [M+H]⁺ 333.2595; found333.2598.

Compound 31

2-(1-(6-methoxynaphthalen-2-yl)ethyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S18), MgBr₂.OEt₂ (52 mg, 0.2 mmol, 1 equiv) and suspension A(NiCl₂.6H₂O/di-MeObipy in THF). Purification by flash columnchromatography (silica gel, hexanes to 1:25 Et₂O:hexanes) afforded 31(50.0 mg, 80%).

Physical State: white solid;

m.p.=82-84° C.;

R_(f)=0.62 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.64-7.67 (m, 2H), 7.57 (s, 1H), 7.35 (dd,J=8.4, 1.8 Hz, 1H), 7.09-7.11 (m, 2H), 3.90 (s, 3H), 2.57 (q, J=7.2 Hz,1H), 1.41 (d, J=7.2 Hz, 3H), 1.21 (s, 6H), 1.20 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 157.1, 140.3, 132.8, 129.5, 129.1, 127.8,126.7, 125.3, 118.5, 105.8, 83.5, 55.4, 24.8, 24.8, 17.1 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₂₆BO₃ [M+H]⁺ 313.1969; found313.1970.

Compound 32

1,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)heptane (32)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S19) and solution B (NiCl₂.6H₂O (20 mol %)/di-MeObipy (26% mol %) inDMF (0.8 mL)). Purification by flash column chromatography (silica gel,hexanes to 1:20 Et₂O:hexanes) afforded 32 (26.5 mg, 38%).

Physical State: colorless oil;

R_(f)=0.45 (silica gel, 1:8 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 1.41-1.36 (m, 4H), 1.29-1.24 (m, 6H), 1.24(s, 24H), 0.75 (t, J=7.8 Hz, 4H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 83.0, 32.5, 29.4, 25.0, 24.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₃₉B₂O₄ [M+H]⁺ 353.3029; found353.3030.

Compound 33

N,N-bis(2-chloroethyl)-4-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl)aniline 33)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S20) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:19 EtOAc:hexanes)afforded 33 (20.7 mg, 26%).

Physical State: yellow oil;

R_(f)=0.36 (silica gel, 1:9 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.09-7.04 (m, 2H), 6.63-6.59 (m, 2H), 3.69(t, J=7.1 Hz, 4H), 3.61 (t, J=7.1 Hz, 4H), 2.54-2.48 (t, J=7.8 Hz, 2H),1.68 (p, J=7.8 Hz, 2H), 1.24 (s, 12H), 0.81 (t, J=7.8 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 144.2, 132.2, 129.9, 112.2, 83.1, 53.8,40.7, 37.6, 26.5, 25.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₃₁BCl₂NO₂ [M+H]⁺ 386.1819; found386.1815.

Compound 34

phenyl(3-(1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)ethyl)phenyl)methanone (34)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S21), MgBr₂.OEt₂ (52 mg, 0.2 mmol, 1 equiv) and suspension A(NiCl₂.6H₂O/di-MeObipy in THF). Purification by flash columnchromatography (silica gel, hexanes to 1:15 EtOAc:hexanes) afforded 34(51.9 mg, 77%).

Physical State: colorless oil;

R_(f)=0.45 (silica gel, 1:6 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.83-7.81 (m, 2H), 7.66 (t, J=1.8 Hz, 1H),7.59-7.56 (m, 2H), 7.49-7.44 (m, 3H), 7.38 (t, J=7.8 Hz, 1H), 2.51 (q,J=7.8 Hz, 1H), 1.35 (d, J=7.8 Hz, 3H), 1.21 (s, 6H), 1.21 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 197.2, 145.4, 138.0, 137.7, 132.4, 132.2,130.3, 129.7, 128.4, 128.3, 127.2, 83.6, 24.8, 24.8, 17.1 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₁H₂₆BO₃ [M+H]⁺ 337.1969; found337.1971.

Compound 35

4,4,5,5-tetramethyl-2-(1-(3-phenoxyphenyl)ethyl)-1,3,2-dioxaborolane(35)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S22), MgBr₂.OEt₂ (52 mg, 0.2 mmol, 1 equiv) and suspension A(NiCl₂.6H₂O/di-MeObipy in THF). Purification by flash columnchromatography (silica gel, hexanes to 1:30 Et₂O:hexanes) afforded 35(52.6 mg, 81%).

Physical State: colorless oil;

R_(f)=0.50 (silica gel, 1:12 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.32 (t, J=7.8 Hz, 2H), 7.22 (t, J=7.8 Hz,1H), 7.07 (t, J=7.8 Hz, 1H), 7.01 (d, J=7.2 Hz, 2H), 6.97 (d, J=7.2 Hz,1H), 6.91 (t, J=1.8 Hz, 1H), 6.79 (dd, J=7.8 Hz, 2.4 Hz, 1H), 2.42 (q,J=7.8 Hz, 1H), 1.31 (d, J=7.8 Hz, 3H), 1.20 (s, 6H), 1.19 (s, 6H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 157.7, 157.2, 147.3, 129.7, 129.6, 123.0,123.0, 118.8, 118.7, 115.9, 83.5, 24.8, 24.7, 17.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₀H₂₆BO₃ [M+H]⁺ 325.1969; found325.1970.

Compound 36

1-(2-((4R,6S)-2,2-dimethyl-6-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)methyl)-1,3-dioxan-4-yl)ethyl)-5-(4-fluorophenyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S23) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:9 EtOAc:hexanes)afforded 36 (77.4 mg, 57%).

Physical State: white foam;

R_(f)=0.52 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.21-7.14 (m, 9H), 7.07 (br d, J=8.4 Hz, 2H),7.00-6.97 (m, 3H), 6.85 (br s, 1H), 4.08-4.03 (m, 1H), 4.00-3.96 (m,1H), 3.85-3.80 (m, 1H), 3.69-3.65 (m, 1H), 3.60-3.55 (m, 1H), 1.68-1.64(m, 2H), 1.55 (d, J=1.8 Hz, 3H), 1.53 (d, J=1.8 Hz, 3H), 1.34 (dt,J=13.2 Hz, 1.2 Hz, 1H), 1.34 (s, 3H), 1.30 (s, 3H), 1.23 (s, 12H),1.08-1.03 (m, 2H), 0.98-0.94 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 165.0, 162.4 (d, J=247.6 Hz), 141.7, 138.6,134.8, 134.5, 133.3 (d, J=8.2 Hz), 130.7, 128.9, 128.8, 128.5, 128.4 (d,J=3.8 Hz), 126.7, 123.8, 123.6, 121.8, 119.7, 115.4 (d, J=21.3 Hz),98.6, 83.3, 66.7, 66.7, 41.0, 38.4, 38.3, 30.3, 26.2, 24.9, 24.9, 21.9,21.7, 20.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₄₁H₅₁BFN₂O₅[M+H]⁺ 681.3870; found681.3870;

[α]D²⁰=+4.0 (c 0.68, CHCl₃).

Compound 37

(4-chlorophenyl)(5-methoxy-2-methyl-3-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)methyl)-1H-indol-1-yl)methanone(37)

On 0.1 mmol scale, General Procedure C was followed with NHPI ester(S37) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, hexanes to 1:17 EtOAc:hexanes)afforded 37 (22.1 mg, 50%).

Physical State: yellow oil;

R_(f)=0.5 (silica gel, 1:4 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.64 (dt, J=9.0 Hz, 1.8 Hz, 2H), 7.45 (m, dt,J=8.4 Hz, 1.8 Hz, 2H), 6.96-6.93 (m, 2H), 6.64 (dd, J=9.0 Hz, 2.6 Hz,1H), 3.84 (s, 3H), 2.29 (s, 3H), 2.18 (s, 2H), 1.23 (s, 12H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 168.3, 156.0, 138.8, 134.7, 133.2, 132.0,131.2, 131.1, 129.1, 116.7, 115.0, 111.3, 101.7, 83.7, 55.8, 29.9, 25.0,13.9 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₄H₂₈BClNO₄ [M+H]⁺ 440.1794; found440.1794.

Compound 38

(5S,8R,9S,10S,13R,14S,17R)-10,13-dimethyl-17-((R)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)butan-2-yl)dodecahydro-3H-cyclopenta[a]phenanthrene-3,7,12(2H,4H)-trione(38)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S38) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:5 EtOAc:hexanes)afforded 38 (63.0 mg, 65%).

Physical State: white solid;

R_(f)=0.40 (silica gel, 1:3 EtOAc:hexanes);

m.p.=230-232° C.;

¹H NMR (600 MHz, CDCl₃): δ 2.92-2.82 (m, 3H), 2.35-2.19 (m, 6H),2.14-2.09 (m, 2H), 2.05-1.94 (m, 4H), 1.80-1.85 (m, 1H), 1.56-1.63 (m,2H), 1.39 (s, 3H), 1.35-1.12 (m, 16H), 1.06 (s, 3H), 0.87-0.81 (m, 4H),0.68-0.62 (m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 212.1, 209.2, 208.9, 83.0, 57.1, 51.9, 49.2,47.0, 45.8, 45.7, 45.1, 42.9, 38.8, 38.2, 36.6, 36.1, 35.4, 29.4, 27.8,25.4, 25.0, 24.9, 22.1, 18.6, 12.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₉H₄₅BO₅ [M+H]⁺ 485.3433; found485.3435.

[α]D²⁰=+16.9 (c 0.62, CHCl₃).

Compound 39

(3S,4aR,6aR,6bS,8aR,11S,12aR,14aR,14bS)-4,4,6a,6b,8a,11,14b-heptamethyl-14-oxo-11-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,14,14a,14b-icosahydropicen-3-ylacetate (39)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S24) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, 1:12:3 EtOAc:hexanes:CH₂Cl₂)afforded 39 (82.0 mg, 69%, d.r.=11.8:1).

Physical State: colorless film;

R_(f)=0.34 (silica gel, 1:5 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): Major isomer δ 5.57 (s, 1H), 4.51 (dd, J=11.8,4.7 Hz, 1H), 2.79 (dt, J=13.7, 3.6 Hz, 1H), 2.35 (s, 1H), 2.20 (ddd,J=13.3, 4.4, 1.7 Hz, 1H), 2.12 (td, J=13.7, 4.6 Hz, 1H), 2.04 (s, 3H),1.96 (t, J=13.6 Hz, 1H), 1.80 (td, J=13.7, 4.6 Hz, 1H), 1.75-1.38 (m,7H), 1.37 (s, 3H), 1.27-1.13 (m, 5H), 1.20 (d, J=1.8 Hz, 12H), 1.15 (s,3H), 1.12 (s, 3H), 1.02 (td, J=13.5, 3.6 Hz, 1H), 0.99 (s, 3H), 0.94(ddt, J=13.7, 4.5, 2.2 Hz, 1H), 0.87 (s, 6H), 0.84 (s, 3H), 0.81-0.76(m, 1H) ppm;

¹³C NMR (151 MHz, CDCl₃): Major isomer δ 200.1, 171.1, 171.1, 128.3,83.0, 80.8, 61.8, 55.2, 45.5, 45.3, 43.6, 38.9, 38.5, 38.2, 37.1, 34.2,32.9, 32.7, 29.1, 28.2, 27.8, 26.7, 26.6, 24.8, 24.7, 23.7, 23.4, 21.5,18.9, 17.7, 17.6, 16.8, 16.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₃₇H₆₀BO₅ [M+H]⁺ 595.4528; found595.4520;

[α]D²⁰=+65.8 (c 1.0, CHCl₃).

Compound 40

(2S,4aR,6aS,6bR,8aR,10S,12aS,12bR,14bR)-10-hydroxy-2,4a,6a,6b,9,9,12a-heptamethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,14b-octadecahydropicen-13(2H)-one(40)

On 0.2 mmol scale, General Procedure C was followed with NHPI ester(S39) and suspension A (NiCl₂.6H₂O/di-MeObipy in THF). Purification byflash column chromatography (silica gel, first flash columnchromatography: 1:5.7 to 1:4 EtOAc:hexanes; second flash columnchromatography, 1:6:3 to 2:6:3 EtOAc:hexanes:CH₂Cl₂) afforded 40 (72.1mg, 65%, d.r.=11.3:1).

Physical State: colorless film;

R_(f)=0.46 (silica gel, 3:7 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): Major isomer δ 5.59 (s, 1H), 3.27-3.18 (m, 1H),2.81 (dt, J=13.5, 3.6 Hz, 1H), 2.36 (s, 1H), 2.22 (ddd, J=13.5, 4.5, 1.7Hz, 1H), 2.14 (td, J=13.7, 4.6 Hz, 1H), 1.99 (t, J=13.6 Hz, 1H), 1.83(td, J=13.7, 4.7 Hz, 1H), 1.74-1.58 (m, 4H), 1.55 (td, J=13.8, 4.0 Hz,1H), 1.51-1.35 (m, 2H), 1.41 (s, 3H), 1.33-1.15 (m, 7H), 1.22 (s, 6H),1.22 (s, 6H), 1.15 (s, 3H), 1.15 (s, 3H), 1.02 (s, 3H), 1.01 (s, 3H),1.00-0.94 (m, 1H), 0.86 (s, 3H), 0.82 (s, 3H), 0.71 (dd, J=11.8, 1.9 Hz,1H) ppm;

¹³C NMR (151 MHz, CDCl₃): Major isomer δ 200.3, 171.1, 128.3, 83.0,79.0, 61.9, 55.2, 45.5, 45.3, 43.6, 39.3, 39.3, 38.5, 37.2, 34.2, 33.0,32.7, 29.1, 28.3, 27.8, 27.5, 26.7, 26.6, 24.8, 24.7, 23.5, 18.9, 17.7,16.5, 15.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₃₅H₅₈BO₄ [M+H]⁺ 553.4422; found553.4423;

[α]D²⁰=+73.4 (c 1.0, CHCl₃).

Compound 40a

(3S,4aR,6aR,6bS,8aR,11S,12aR,14aR,14bS)-4,4,6a,6b,8a,11,14b-heptamethyl-14-oxo-11-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,14,14a,14b-icosahydropicen-3-yl3,5-dinitrobenzoate (40a)

A culture tube charged with 40 (30 mg, 0.054 mmol, 1.0 equiv.),3,5-dinitrobenzoyl chloride (50 mg, 0.22 mmol, 4.1 equiv.), and DMAP(1.3 mg, 0.011 mmol, 0.2 equiv.). CH₂Cl₂ (0.3 mL) and Et₃N (30 μL, 0.22mmol, 4.1 mmol) were added, and the resulting mixture was stirred for 1h at room temperature. The mixture was loaded directly onto a silica gelcolumn for purification by flash column chromatography (1:11EtOAc:hexanes) to afford 40a (39.0 mg, 96%, d.r.=11.3:1). The pureproduct was crystallized from hexanes/CH₂Cl₂.

Physical State: pale yellow solid (major isomer is a white solid);

m.p. decompose at 295° C.;

R_(f)=0.45 (silica gel, 1:5.7 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): Major isomer δ 9.22 (t, J=2.2 Hz, 1H), 9.13 (d,J=2.2 Hz, 2H), 5.60 (s, 1H), 4.88 (dd, J=11.9, 4.7 Hz, 1H), 2.92 (dt,J=13.7, 3.6 Hz, 1H), 2.40 (s, 1H), 2.26-2.19 (m, 1H), 2.13 (td, J=13.7,4.5 Hz, 1H), 1.98 (t, J=13.6 Hz, 1H), 1.95-1.87 (m, 1H), 1.87-1.75 (m,2H), 1.74-1.59 (m, 3H), 1.56-1.48 (m, 2H), 1.45 (dt, J=12.8, 3.1 Hz,1H), 1.40 (s, 3H), 1.30-1.09 (m, 5H), 1.23 (s, 3H), 1.21 (s, 6H), 1.21(s, 6H), 1.16 (s, 3H), 1.08 (s, 3H), 1.00 (s, 3H), 0.97 (s, 3H),0.97-0.94 (m, 1H), 0.89 (dd, J=11.8, 1.9 Hz, 1H), 0.86 (s, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): Major isomer δ 199.9, 171.4, 162.3, 148.8,134.8, 129.5, 128.3, 122.4, 84.3, 83.1, 61.7, 55.3, 45.6, 45.3, 43.6,38.9, 38.6, 38.5, 37.1, 34.2, 32.8, 32.7, 29.2, 28.5, 27.8, 26.7, 26.6,24.8, 24.7, 23.8, 23.4, 18.9, 17.7, 17.6, 17.2, 16.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₄₂H₆₀BN₂O₉[M+H]⁺ 747.4386; found747.4385;

[α]D²⁰=+60.5 (c 1.0, CHCl₃).

Compound 41

(E)-7-hydroxy-5-methoxy-4-methyl-6-(3-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pent-2-en-1-yl)isobenzofuran-1(3H)-one(41)

On 0.2 mmol scale, General Procedure B was followed with NHPI ester(S25) and solution B (NiCl₂.6H₂O/di-MeObipy in DMF). Purification byflash column chromatography (silica gel, hexanes to 1:6:6EtOAc:hexanes:CH₂Cl₂) afforded 41 (37.0 mg, 46%).

Physical State: white solid;

m.p.=122-124° C.;

R_(f)=0.40 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.64 (s, 1H), 5.21-5.18 (m, 3H), 3.75 (s,3H), 3.37 (d, J=6.6 Hz, 2H), 2.13 (s, 3H), 2.08 (t, J=7.8 Hz, 2H), 1.77(s, 3H), 1.17 (s, 12H), 0.86 (t, J=7.8 Hz, 2H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 173.1, 163.9, 153.8, 143.9, 137.8, 122.8,120.6, 116.8, 106.4, 83.0, 70.1, 61.1, 33.6, 24.9, 22.7, 16.3, 11.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₂H₃₂BO₆ [M+H]⁺ 403.2286; found403.2289.

Experimental Procedure and Characterization Data for Boronic AcidsCompound 4a

(4-phenylbutyl)boronic acid (4a)

Pinacol boronate ester 4 (70 mg, 0.27 mmol) was dissolved in CH₂Cl₂ (5mL) under argon and the solution was cooled to −78° C. in a dryice/acetone bath. BCl₃ (0.81 mL, 1.0 M in CH₂Cl₂, 3.0 equiv) was addeddropwise, after which the mixture was stirred for 1 h at −78° C. Themixture was then allowed to warm up to room temperature, and thevolatiles were removed in vacuo. Anhydrous methanol (5 mL) was added andthe resulting mixture was stirred for 10 minutes when methanol wasremoved in vacuo. An additional portion of methanol (5 mL) was added;the mixture was stirred for 10 minutes before it is concentrated invacuo. This process was repeated for additional three times. Theresulting crude product was then purified with preparative thin layerchromatography to afford 4a as a white solid (41.8 mg, 87%).

¹H NMR (600 MHz, DMSO-d₆/D₂O 100/1): δ 7.28-7.22 (m, 2H), 7.15 (ddt,J=13.9 Hz, 6.9 Hz, 1.5 Hz, 3H), 2.56-2.51 (m, 2H), 1.51 (tt, J=7.8, 6.7Hz, 2H), 1.38-1.28 (m, 2H), 0.60 (t, J=7.9 Hz, 2H).

¹³C NMR (151 MHz, DMSO-d₆/D₂O 100/1): δ 142.60, 128.32, 128.27, 125.58,35.26, 34.21, 23.98, 15.27 (br);

HRMS (ESI-TOF) Calcd for C₁₀H₁₆BO₂ [M+H]⁺ 179.1238; found 179.1236.

Compound 3a

(4-phenylbutan-2-yl)boronic acid (3a)

Pinacol boronate ester 3 (30 mg, 0.12 mmol) was dissolved in CH₂Cl₂ (2mL) under argon and the solution was cooled to −78° C. in a dryice/acetone bath. BCl₃ (0.36 mL, 1.0 M in CH₂Cl₂, 3.0 equiv) was addeddropwise, after which the mixture was stirred for 1 h at −78° C. Themixture was then allowed to warm up to room temperature, and thevolatiles were removed in vacuo. Anhydrous methanol (5 mL) was added andthe resulting mixture was stirred for 10 minutes before methanol wasremoved in vacuo. An additional portion of methanol (5 mL) was added;the mixture was stirred for 10 minutes before it was concentrated invacuo. This process was repeated for additional three times. Theresulting crude product was then purified with preparative thin layerchromatography to afford 4a as a white solid (15.4 mg, 75%).

¹H NMR (600 MHz, DMSO-d₆/D₂O 100/1): δ 7.24 (t, J=7.6 Hz, 2H), 7.18-7.10(m, 3H), 2.53-2.48 (m, 2H), 1.74-1.63 (m, 1H), 1.42 (ddt, J=13.0 Hz, 9.9Hz, 6.5 Hz, 1H), 0.90 (d, J=7.2 Hz, 3H), 0.89-0.81 (m, 1H) ppm;

¹³C NMR (151 MHz, DMSO-d₆/D₂O 100/1): δ 143.03, 128.34, 125.61, 35.65,35.05, 20.33 (br), 16.35 ppm;

HRMS (ESI-TOF) Calcd for C₁₀H₁₆BO₂ [M+H]⁺ 179.1238; found 179.1232.

Compound 33a

(3-(4-(bis(2-chloroethyl)amino)phenyl)propyl)boronic acid (33a)

To a solution of pinacol boronate ester 34 (76.2 mg, 0.2 mmol) in CH₂Cl₂(1 mL) was added BCl₃ (0.79 mL, 1.0 M in CH₂Cl₂) dropwise at −78° C. Thereaction mixture was stirred at −78° C. for 30 minutes followed byanother 30 minutes at room temperature. The reaction was quenched withmethanol (2 mL) and was concentrated in vacuo. To the residue was addedMeOH (2 mL) which was subsequently removed in vacuo; this process wasrepeated for additional three times. Purification of the resultingresidue by preparative reverse-phase HPLC (20-80% CH₃CN/H₂O over 30 min,both CH₃CN and H₂O containing 0.1% TFA) afforded 33a (27 mg, 50%) as acolorless oil.

¹H NMR (600 MHz, DMSO-d₆/D₂O 10/1): δ 7.00 (d, J=12.6 Hz, 2H), 6.65 (d,J=12.6 Hz, 2H), 3.71-3.65 (m, 8H), 2.39 (t, J=7.8 Hz, 2H), 1.58-1.53 (m,2H), 0.59 (t, J=8.4 Hz, 2H) ppm;

¹³C NMR (151 MHz, DMSO-d₆/D₂O 10/1): δ 144.2, 130.9, 129.3, 111.8, 52.3,41.2, 37.2, 26.6 ppm;

HRMS (ESI-TOF) Calcd for C₁₃H₂₁BCl₂NO₂ [M+H]⁺ 304.1037; found 304.1030.

Compound S41

(2,5-dichlorobenzoyl)glycylleucine (S41)

Deprotection of Boc:

To a solution of Boc-Gly-Leu-OMe¹¹ (3.1 g, 10.26 mmol) in CH₂Cl₂ (30 mL)was added TFA (15 mL) at room temperature, the reaction mixture wasstirred for 1 h before concentrated in vacuo. The residue was useddirectly in the next step.

Amide Bond Formation:

To a solution 2,5-dichlorobenonic acid (2.94 g, 15.4 mmol) in THF (70mL) was added 4-methylmorpholine (4.0 mL, 35.9 mmol) at −15° C., thereaction mixture was stirred for 10 min at that temperature. To theresulting white suspension was added isobutyl chloroformate (2.0 mL,15.4 mmol) dropwise and the mixture was stirred for another 30 min at−15° C. The crude TFA salt (from the deprotection step) in THF (35 mL)was added slowly at the same temperature. The reaction mixture waswarmed up to room temperature and stirred for 6 h. The resulting mixturewas diluted with EtOAc (100 mL), washed with water (100 mL), sat.aqueous NaHCO₃ (100 mL), and brine (100 mL). The combined organic layerwas dried over anhydrous Na₂SO₄, filtered, and concentrated.Purification by a flash column chromatography (silica, 3:2 Hexane/EtOAc)afforded the desired ester which is not very pure but can be used innext step without further purification.

Hydrolysis of Methyl Ester:

To a solution of the aforementioned ester in THF (50 mL) was addedaqueous LiOH (1M, 50 mL). The reaction mixture was stirred at roomtemperature for 2 h and was then washed with EtOAc (60 mL). The aqueouslayer was acidified with 1N HCl (65 mL) and extracted with EtOAc (100mL). The organic layer was washed with brine (100 mL) whereby theaqueous layers were back-extracted with EtOAc (100 mL). The combinedorganic phase was concentrated in vacuo. To the residue was added CH₂Cl₂(30 ml) when the desired product S41 precipitated out and was collectedby filtration (2.31 g, 63% over 3 steps).

m.p.=137-138° C.;

¹H NMR (600 MHz, MeOH-d4): δ 7.63 (dd, J=1.8 Hz, 0.6 Hz, 1H), 7.45-7.48(m, 2H), 4.50 (dd, J=9.6 Hz, 5.4 Hz, 1H), 4.08 (dd, J=37.8 Hz, 16.8 Hz,2H), 1.79-1.72 (m, 1H), 1.70-1.62 (m, 2H), 0.98 (d, J=6.6 Hz, 3H), 0.95(d, J=6.6 Hz, 3H) ppm;

¹³C NMR (151 MHz, MeOH-d4): δ 175.8, 170.9, 168.7, 138.4, 134.0, 132.6,132.3, 130.6, 130.2, 52.1, 43.6, 41.9, 26.0, 23.4, 21.9 ppm;

HRMS (ESI-TOF) Calcd for C₁₅H₁₉Cl₂N₂O₄ [M+H]⁺ 361.0716; found 361.0706;

[α]D²⁰=−14.0 (c 1.0, MeOH).

Compound S42

1,3-dioxoisoindolin-2-yl (2,5-dichlorobenzoyl)glycylleucinate (S42)

On 2.0 mmol scale, general procedure A was followed with S41.Purification by flash column chromatography (deactivated silica gel, 3:7EtOAc:hexanes) furnished S42 (940 mg, 79%).

Physical state: white solid;

m.p.=164° C.;

R_(f)=0.55 (silica gel, 3:2 EtOAc:hexanes);

¹H NMR (600 MHz, THF-d8): δ 8.05 (br s, 1H), 7.99-7.97 (m, 1H),7.91-7.89 (m, 2H), 7.87-7.85 (m, 2H), 7.58 (dd, J=2.4 Hz, 0.5 Hz, 1H),7.42-7.38 (m, 2H), 5.10-5.06 (m, 1H), 4.14 (dd, J=16.8 Hz, 6.0 Hz, 1H),3.99 (dd, J=16.8 Hz, 6.0 Hz, 1H), 1.92-1.83 (m, 2H), 1.80-1.75 (m, 1H),1.02 (d, J=6.0 Hz, 3H), 1.00 (d, J=6.0 Hz, 3H) ppm;

¹³C NMR (151 MHz, THF-d8): δ 170.5, 169.4, 166.0, 162.4, 139.2, 135.9,133.5, 132.3, 131.5, 130.7, 130.5, 130.2, 124.7, 49.7, 43.6, 42.3, 25.8,23.4, 22.1 ppm;

HRMS (ESI-TOF) Calcd for C₂₃H₂₂Cl₂N₃O₆ [M+H]⁺ 506.0880; found 506.0875;

[α]D²⁰=−1.0 (c 1.0, THF).

Compound 1

On 0.2 mmol scale, general procedure C was followed using suspension C(NiCl₂.6H₂O/di-tBubipy in THF) with S42. Flash column chromatography(silica gel, hexanes to 2:3 EtOAc:hexanes to 4:1 EtOAc:hexanes) affordedpinacol aminoboronate ester S43 which was used in the next step withoutfurther purification.

The pinacol aminoboronate ester S43 was dissolved in CH₂Cl₂ (5 mL) underargon and the solution was cooled to −78° C. in a dry ice/acetone bath.BCl₃ (0.6 mL, 1.0 M in CH₂Cl₂, 3.0 equiv.) was added dropwise, afterwhich the mixture was stirred for 1 h at −78° C. The mixture was thenallowed to warm up to room temperature, and the volatiles were removedin vacuo. Anhydrous methanol (5 mL) was added and the mixture wasstirred for 10 minutes when the methanol was removed in vacuo. Anadditional portion of methanol (5 mL) was added; the mixture was stirredfor 10 minutes before it is concentrated in vacuo. This process wasrepeated for three times. The resulting residue was then purified bypreparative reverse-phase HPLC (10-60% CH₃CN/H₂O over 35 min, both CH₃CNand H₂O containing 0.1% TFA) to afford Ninlaro (1, 23.0 mg, 32% over 2steps).

¹H NMR (600 MHz, MeOH-d₄): δ 7.60 (t, J=1.5 Hz, 1H), 7.49-7.47 (m, 2H),4.24 (s, 2H), 2.79 (t, J=7.6 Hz, 1H), 1.68 (ddt, J=14.7 Hz, 13.0 Hz, 6.4Hz, 1H), 1.38 (tdd, J=13.8 Hz, 10.4 Hz, 5.9 Hz, 2H), 0.94 (dd, J=6.6 Hz,1.5 Hz, 6H);

¹³C NMR (151 MHz, MeOH-d₄): δ 175.6, 168.8, 138.0, 134.0, 132.7, 132.5,130.7, 130.2, 44.7 (br, a to boron), 40.9, 40.2, 27.1, 23.7, 22.4.

HRMS (ESI-TOF, m/z): calc'd for C₁₄H₁₈BCl₂N₂O₃ [M−H₂O+H]⁺ 343.0782;found 343.0779;

[α]D²⁰=−0.6 (c 1.0, MeOH).

Decarboxylative Borylation Enabled Late-Stage Diversification of LipitorCompound 36a

5-(4-fluorophenyl)-1-(2-((4R,6R)-6-(hydroxymethyl)-2,2-dimethyl-1,3-dioxan-4-yl)ethyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36a)

To a solution of 36 (50 mg, 0.073 mmol) in THF/H₂O (1:1, 0.73 mL) atroom temperature open to air was added NaBO₃.4H₂O (56 mg, 0.37 mmol).The mixture was stirred vigorously for 3 h before H₂O (10 mL) was added.The resulting mixture was extracted with EtOAc (10 mL×3). The combinedorganic extracts were dried over Na₂SO₄, filtered, and concentrated.Purification by flash column chromatography (silica gel, 2:3EtOAc:hexanes) afforded 36a (40 mg, 86%).

m.p.=166-170° C.;

R_(f)=0.27 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.21-7.15 (m, 9H), 7.07 (d, J=8.0 Hz, 2H),7.02-6.96 (m, 3H), 6.86 (s, 1H), 4.13-4.05 (m, 1H), 3.92-3.81 (m, 2H),3.73-3.66 (m, 1H), 3.61-3.52 (m, 2H), 3.45 (dd, J=11.4 Hz, 6.1 Hz, 1H),1.74-1.61 (m, 2H), 1.54 (s, 3H), 1.53 (s, 3H), 1.37 (s, 3H), 1.34 (s,3H), 1.74-1.61 (m, 2H);

¹³C NMR (151 MHz, CDCl₃): δ 164.9, 162.4 (d, J=247.6 Hz), 141.7, 138.5,134.8, 133.3 (d, J=8.0 Hz), 130.6, 128.9, 128.8, 128.5, 128.4 (d, J=3.5Hz), 126.7, 123.6, 121.9, 119.7, 115.5 (d, J=21.4 Hz), 98.9, 69.4, 66.2,66.0, 41.0, 38.3, 31.9, 30.0, 26.2, 21.9, 21.7, 20.0;

¹⁹F NMR (376 MHz, acetone-d6): δ −114.00 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₃₅H₄₀FN₂O₄[M+H]⁺ 571.2966; found571.2963;

[α]D²⁰=−4.6 (c 1.0, CHCl₃).

Compound 36b

tert-butyl(((4R,6R)-6-(2-(2-(4-fluorophenyl)-5-isopropyl-3-phenyl-4-(phenylcarbamoyl)-1H-pyrrol-1-yl)ethyl)-2,2-dimethyl-1,3-dioxan-4-yl)methyl)carbamate(36b)

The amination was performed following the literature procedure¹² withslight modifications. A solution of O-methylhydroxylamine (63 pL, 2.8 Min THF, 6.0 equiv) was diluted with THF (1 mL). n-BuLi (72 μL, 2.45 M inhexanes, 6.0 equiv) was added at −78° C., and the resulting mixture wasstirred for 1 h at that temperature. A solution of pinacol boronate 36(20 mg, 0.03 mmol) in THF (1 mL) was added dropwise at −78° C. Afterwarming up to room temperature, the reaction mixture was heated to 65°C. and stirred for 36 h. Upon cooling to room temperature, Boc₂O (66 mg,10.0 equiv) was added. The resulting mixture was stirred at roomtemperature for 1 h before the volatiles were removed in vacuo.Purification of the resulting residue by preparative thin layerchromatography (silica gel, 15:1 DCM:Et₂O) afforded 36b (10.7 mg, 54%)as colorless oil.

Physical state: colorless oil;

R_(f)=0.4 (silica gel, 1:3 hexane: EtOAc);

¹H NMR (600 MHz, CDCl₃): δ 7.24-7.09 (m, 9H), 7.07 (d, J=8.0 Hz, 2H),7.04-6.94 (m, 3H), 6.86 (s, 1H), 4.84 (s, 1H), 4.07 (ddd, J=15.3 Hz,10.7 Hz, 5.1 Hz, 1H), 3.82 (ddt, J=15.1 Hz, 10.3 Hz, 6.5 Hz, 2H), 3.66(tt, J=8.2 Hz, 3.6 Hz, 1H), 3.57 (p, J=7.2 Hz, 1H), 3.24 (d, J=8.7 Hz,1H), 2.98 (ddd, J=13.8 Hz, 6.8 Hz, 5.1 Hz, 1H), 1.70-1.63 (m, 2H), 1.53(d, J=7.1 Hz, 6H), 1.44 (s, 9H), 1.34 (s, 3H), 1.31 (s, 3H), 1.27-1.20(m, 1H), 1.07 (q, J=12.0 Hz, 1H);

¹³C NMR (151 MHz, CDCl₃): δ 164.9, 162.4 (d, J=247.9 Hz), 156.2, 141.6,138.5, 134.8, 133.3 (d, J=8.1 Hz), 130.6, 128.9, 128.8, 128.5, 128.4 (d,J=3.5 Hz), 126.7, 123.6, 121.9, 119.7, 115.5 (d, J=21.3 Hz), 98.8, 79.6,68.2, 66.3, 45.4, 41.0, 38.3, 33.4, 30.5, 30.0, 28.5, 26.2, 21.9, 21.7,20.0;

¹⁹F NMR (376 MHz, CDCl₃): δ −113.93 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₄₀H₄₉FN₃O₅[M+H]⁺ 670.3651; found670.3646;

[α]D²⁰=−2.0 (c 0.74, CHCl₃).

Compound 36c

1-(2-((4R,6R)-2,2-dimethyl-6-(thiophen-2-ylmethyl)-1,3-dioxan-4-yl)ethyl)-5-(4-fluorophenyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36c)

To a solution of thiophene (23 μL, 0.28 mmol) in THF (1.0 mL) was addedn-BuLi (0.1 mL, 2.5 M in hexanes, 0.25 mmol) at −78° C. The resultingmixture was warmed to room temperature and stirred for 1 h when some ofthe resulting yellow solution (0.33 mL) was transferred to a reactiontube. A solution of 36 (12.4 mg, 0.018 mmol) in THF (0.3 mL) was addeddropwise at −78° C. The resulting mixture was stirred at the sametemperature for 1.5 h when a solution of NBS (14.4 mg, 0.081 mmol) inTHF (0.3 mL) was added. After stirring for 1 h at the same temperature,the reaction was quenched with sat. aqueous Na₂S₂O₃ (1 mL) beforewarming up to room temperature. The resulting mixture was extracted withEtOAc (1 mL×3). The combined organic layers were dried over anhydrousNa₂SO₄ and concentrated in vacuo. Purification by flash columnchromatography (silica gel, 1:9 EtOAc:hexanes) and PTLC (silica gel, 1:6EtOAc:hexanes) afforded 36c (6.5 mg, 56%).

Physical state: white foam;

R_(f)=0.61 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, acetone-d6): δ 8.29 (br s, 1H), 7.45 (d, J=7.8 Hz, 2H),7.30-7.27 (m, 2H), 7.24 (dd, J=5.4 Hz, 1.2 Hz, 1H), 7.20 (t, J=7.8 Hz,2H), 7.13-7.09 (m, 6H), 7.08-7.05 (m, 1H), 6.99-6.96 (m, 1H), 6.92 (dd,J=5.4 Hz, 3.6 Hz, 1H), 6.85-6.84 (m, 1H), 4.11-4.06 (m, 1H), 4.05-4.00(m, 1H), 3.91-3.86 (m, 1H), 3.85-3.81 (m, 1H), 3.43-3.39 (m, 1H),2.93-2.90 (m, 1H), 2.87-2.83 (m, 1H), 1.75-1.63 (m, 2H), 1.47 (d, J=1.2Hz, 3H), 1.45 (d, J=1.2 Hz, 3H), 1.36 (dt, J=12.6 Hz, 3.0 Hz, 1H), 1.36(s, 3H), 1.28 (s, 3H) 1.05-0.99 (m, 1H) ppm;

¹³C NMR (151 MHz, acetone-d6): δ 166.4, 163.1 (d, J=245.6 Hz), 140.9,140.6, 139.4, 136.1, 134.5 (d, J=8.2 Hz), 130.8, 129.9 (d, J=3.3 Hz),129.3, 128.9, 128.6, 127.3, 126.7, 126.7, 124.9, 123.8, 122.4, 120.2,118.0, 116.0 (d, J=21.6 Hz), 99.2, 70.2, 67.3, 41.3, 39.1, 37.3, 36.5,30.5, 26.9 22.4, 22.3, 20.1 ppm;

¹⁹F NMR (376 MHz, acetone-d6): δ −114.91 ppm;

HRMS (ESI-TOF) Calcd for C₃₉H₄₂FN₂O₃S [M+H]⁺ 637.2895; found 637.2892;

[α]D²⁰=+19.2 (c 0.5, CHCl₃).

Compound 36d

1-(2-((4R,6R)-6-(benzofuran-2-ylmethyl)-2,2-dimethyl-1,3-dioxan-4-yl)ethyl)-5-(4-fluorophenyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36d)

To a solution of 2,3-benzofuran (30 μL, 0.27 mmol) in THF (1.0 mL) wasadded n-BuLi (0.1 mL, 2.5 M in hexanes, 0.25 mmol) at −78° C. Theresulting solution was warmed up to room temperature. The resultingmixture was warmed to room temperature and stirred for 1 h when some ofthe resulting yellow solution (0.33 mL) was transferred to a reactiontube. A solution of 36 (12.0 mg, 0.018 mmol) in THF (0.3 mL) was addeddropwise at −78° C. The resulting mixture was stirred at the sametemperature for 1 h when a solution of NBS (14.4 mg, 0.081 mmol) in THF(0.3 mL) was added. After stirring for 1 h at the same temperature, thereaction was quenched with sat. aqueous Na₂S₂O₃ (1 mL) before warming upto room temperature. The resulting mixture was extracted with EtOAc (1mL×3). The combined organic layers were dried over anhydrous Na₂SO₄ andconcentrated in vacuo. Purification by flash column chromatography(silica gel, 1:9 EtOAc:hexanes) and preparative thin layerchromatography (silica gel, 1:9 EtOAc:hexanes) afforded 36d (6.1 mg,52%).

Physical state: colorless oil;

R_(f)=0.64 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, acetone-d6): δ 8.29 (br s, 1H), 7.54-7.52 (m, 1H), 7.44(d, J=7.8 Hz, 2H), 7.45-7.42 (m, 1H), 7.31-7.27 (m, 2H), 7.24-7.17 (m,4H), 7.13-7.05 (m, 7H), 6.99-6.96 (m, 1H), 6.58 (dd, J=1.2 Hz, 0.6 Hz,1H), 4.29-4.24 (m, 1H), 4.11-4.06 (m, 1H), 3.91-3.85 (m, 2H), 3.44-3.37(m, 1H), 2.93 (dd, J=15.6 Hz, 6.6 Hz, 1H), 2.79 (dd, J=15.6 Hz, 6.6 Hz,1H), 1.76-1.65 (m, 2H), 1.46 (s, 3H), 1.45 (s, 3H), 1.46-1.51 (m, 1H),1.39 (d, J=0.6 Hz, 3H), 1.27 (d, J=0.6 Hz, 3H), 1.14-1.08 (m, 1H) ppm;

¹³C NMR (151 MHz, acetone-d6): δ 166.4, 163.1 (d, J=245.7 Hz), 156.5,155.5, 140.6, 139.4, 136.1, 134.5 (d, J=8.3 Hz), 130.8, 129.9 (d, J=3.3Hz), 129.9, 129.3, 128.9, 128.6, 126.7, 124.2, 123.8, 123.4, 122.4,121.3, 120.2, 120.1, 118.0, 116.0 (d, J=21.6 Hz), 111.4, 104.6, 99.3,68.1, 67.3, 41.3, 39.1, 37.0, 36.2, 30.4, 26.9, 22.4, 22.3, 20.1 ppm;¹⁹F NMR (376 MHz, acetone-d6): 5-114.95 ppm;

HRMS (ESI-TOF) Calcd for C₄₃H₄₄FN₂O₄[M+H]⁺ 671.3280; found 671.3274;

[α]D²⁰=+28.5 (c 0.5, CHCl₃).

Compound 36e

1-(2-((4R,6S)-6-((3-chloropyridin-2-yl)methyl)-2,2-dimethyl-1,3-dioxan-4-yl)ethyl)-5-(4-fluorophenyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36e)

To a screw-capped culture tube was added Pd₂(dba)₃ (1.9 mg, 0.0022 mmol,0.1 equiv), p-anisyldiphenylphosphine (3.7 mg, 0.0132 mmol, 0.6 equiv),1-chloro-4-nitrobenzene (35 mg, 0.22 mmol, 10 equiv), and K₃PO₄ (47 mg,0.22 mmol, 10 equiv). This tube was then evacuated and backfilled withargon for three times. 1,4-dioxane (0.4 mL) was then added via a syringeand the resulting mixture was stirred at room temperature for 5 minutes.A solution of 36 (15.0 mg, 0.022 mmol) in dioxane (0.6 mL) and degassedDI water (0.5 mL) were added sequentially. The reaction mixture washeated at 100° C. for 15 h, after which it was cooled to roomtemperature and treated with brine (4 mL). The resulting mixture wasextracted with EtOAc (2 mL×3). The combined organic layers were driedover anhydrous Na₂SO₄ and concentrated in vacuo. Purification by flashcolumn chromatography (silica gel, 1:6 to 3:7 EtOAc:hexanes) and PTLC(silica gel, 1:3 EtOAc:hexanes) afforded 36e (7.9 mg, 54%).

Physical state: colorless oil;

R_(f)=0.38 (silica gel, 3:7 EtOAc:hexanes);

¹H NMR (600 MHz, acetone-d6): δ 8.45 (dd, J=4.8 Hz, 1.8 Hz, 1H), 8.30(br s, 1H), 7.79 (dd, J=8.4 Hz, 1.8 Hz, 1H), 7.45 (d, J=7.8 Hz, 2H),7.30-7.25 (m, 3H), 7.20 (t, J=7.8 Hz, 2H), 7.12-7.05 (m, 7H), 6.99-6.96(m, 1H), 4.46-4.41 (m, 1H), 4.11-4.06 (m, 1H), 3.91-3.86 (m, 1H),3.85-3.81 (m, 1H), 3.44-3.39 (m, 1H), 3.13 (dd, J=14.4 Hz, 6.6 Hz, 1H),2.88 (dd, J=14.4 Hz, 7.2 Hz, 1H), 1.76-1.64 (m, 2H), 1.47 (d, J=0.6 Hz,3H), 1.45 (d, J=0.6 Hz, 3H), 1.38 (dt, J=12.6 Hz, 2.4 Hz, 1H), 1.34 (s,3H), 1.24 (s, 3H), 1.16-1.10 (m, 1H) ppm;

¹³C NMR (151 MHz, acetone-d6): δ 166.4, 163.1 (d, J=245.5 Hz), 156.2,148.3, 140.6, 139.3, 137.6, 136.2, 134.5 (d, J=8.3 Hz), 132.2, 130.8,129.9 (d, J=3.3 Hz), 129.3, 128.9, 128.6, 126.7, 123.8, 123.8, 122.4,120.2, 118.0, 116.0 (d, J=21.6 Hz), 99.2, 68.7, 67.3, 42.3, 41.3, 39.2,37.0, 30.5, 26.9, 22.4, 22.3, 20.1 ppm;

¹⁹F NMR (376 MHz, acetone-d6): δ −114.92 ppm;

HRMS (ESI-TOF) Calcd for C₄₀H₄₂ClFN₃O₃[M+H]⁺ 666.2893; found 666.2884;

[α]D²⁰=+26.2 (c 0.5, CHCl₃).

Compound 36f

1-(2-((4R,6S)-2,2-dimethyl-6-(4-nitrobenzyl)-1,3-dioxan-4-yl)ethyl)-5-(4-fluorophenyl)-2-isopropyl-N,4-diphenyl-1H-pyrrole-3-carboxamide(36f)

To a screw-capped culture tube was added Pd₂(dba)₃ (1.9 mg, 0.0022 mmol,0.1 equiv), p-anisyldiphenylphosphine (3.7 mg, 0.0132 mmol, 0.6 equiv),1-chloro-4-nitrobenzene (35 mg, 0.22 mmol, 10 equiv), and K₃PO₄ (47 mg,0.22 mmol, 10 equiv). This tube was evacuated and backfilled with argonfor three times. 1,4-dioxane (0.4 mL) was added via a syringe and theresulting mixture was stirred at room temperature for 5 minutes. Asolution of 36 (15.0 mg, 0.022 mmol) in dioxane (0.6 mL) and degassed DIwater (0.5 mL) were added sequentially. The reaction mixture was heatedto 100° C. for 15 h after which it was cooled to room temperature andtreated with brine (4 mL). The resulting mixture was extracted withEtOAc (2 mL×3). The combined organic layers were dried over anhydrousNa₂SO₄ and concentrated in vacuo. Purification by flash columnchromatography (silica gel, 1:9 to 1:3 EtOAc:hexanes) and PTLC (silicagel, 1:4 EtOAc:hexanes) afforded 36f (10.5 mg, 72%).

Physical state: yellow oil;

R_(f)=0.45 (silica gel, 3:7 EtOAc:hexanes);

¹H NMR (600 MHz, acetone-d6): δ 8.28 (br s, 1H), 8.15 (dt, J=9.0 Hz, 1.8Hz, 2H), 7.51 (dt, J=9.0 Hz, 1.8 Hz, 2H), 7.45 (d, J=8.4 Hz, 2H),7.30-7.27 (m, 2H), 7.20 (t, J=7.8 Hz, 2H), 7.14-7.10 (m, 6H), 7.09-7.05(m, 1H), 6.99-6.96 (m, 1H), 4.17-4.13 (m, 1H), 4.11-4.06 (m, 1H),3.92-3.87 (m, 1H), 3.85-3.81 (m, 1H), 3.44-3.37 (m, 1H), 2.87 (dd,J=13.8 Hz, 7.2 Hz, 1H), 2.81 (dd, J=13.8 Hz, 7.2 Hz, 1H), 1.73-1.65 (m,2H), 1.46 (d, J=0.6 Hz, 3H), 1.45 (d, J=0.6 Hz, 3H), 1.36 (dt, J=12.6Hz, 2.4 Hz, 1H), 1.32 (s, 3H), 1.25 (s, 3H), 1.09-1.03 (m, 1H) ppm;

¹³C NMR (151 MHz, acetone-d6): δ 166.4, 163.1 (d, J=245.5 Hz), 147.6,147.5, 140.5, 139.4, 136.1, 134.5 (d, J=8.3 Hz), 131.4, 130.8, 129.9 (d,J=3.8 Hz), 129.3, 128.9, 128.7, 126.7, 123.9, 123.8, 122.4, 120.2,118.0, 116.0 (d, J=21.4 Hz), 99.2, 69.8, 67.3, 42.9, 41.2, 39.1, 36.7,30.4, 26.9, 22.4, 22.3, 20.1 ppm;

¹⁹F NMR (376 MHz, acetone-d6): δ −114.92 ppm;

HRMS (ESI-TOF) Calcd for C₄₁H₄₃FN₃O₅ [M+H]⁺ 676.3181; found 676.3182;

[α]D²⁰=+10.8 (C 0.5, CHCl₃).

Synthesis of Borono-Vancomycin Analog

Compound S45

To S44 [synthesized according to literature report (38, 62)] (600 mg,0.43 mmol, 1.0 equiv.) in CH₃CN (5.1 mL) was addedN-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA, 2.4 mL,10.2 mmol, 23.7 equiv.), the resulting mixture was heated to 50° C.After 30 h, the reaction mixture was poured onto a mixture of sat.aqueous citric acid (50 mL)/EtOAc (20 mL) and stirred vigorously at roomtemperature for 12 h. The organic layer was separated and washed withsat. aqueous NaHCO₃ (50 mL) and brine (50 mL). The aqueous layers werethen back-extracted with EtOAc (20 mL×2). The combined organic layerswere dried over anhydrous Na₂SO₄ and concentrated in vacuo. Purificationby flash column chromatography (silica gel, 1:1 to 4:1 EtOAc:hexanes)and preparative TLC (7:93 MeOH/CH₂Cl₂) afforded the desired product S45(440 mg, 63%).

Physical state: white film;

R_(f)=0.31 (silica gel, 7:93 MeOH/CH₂Cl₂);

¹H NMR (600 MHz, acetone-d₆): δ 9.43 (br s, 1H), 7.94 (d, J=6.5 Hz, 1H),7.57 (dd, J=8.3, 1.9 Hz, 1H), 7.53 (br s, 3H), 7.49 (s, 1H), 7.46 (s,1H), 7.45 (s, 1H), 7.43-7.33 (m, 4H), 7.26 (d, J=8.3 Hz, 1H), 7.19 (d,J=8.3 Hz, 1H), 7.08 (s, 1H), 7.03 (d, J=8.7 Hz, 1H), 6.77 (d, J=9.9 Hz,1H), 6.73 (s, 1H), 6.67 (d, J=2.3 Hz, 1H), 6.45 (br s, 1H), 6.31 (d,J=2.3 Hz, 1H), 5.94 (br s, 1H), 5.85 (s, 1H), 5.58 (d, J=4.9 Hz, 1H),5.54 (s, 1H), 5.51 (s, 1H), 5.39 (d, J=12.3 Hz, 1H), 5.23 (d, J=12.3 Hz,1H), 5.20 (br s, 1H), 5.10 (br s, 1H), 4.96 (d, J=6.5 Hz, 1H), 4.67 (d,J=5.2 Hz, 1H), 4.63 (t, J=7.2 Hz, 1H), 4.42 (d, J=11.7 Hz, 1H), 4.18 (s,3H), 3.68 (s, 3H), 3.67 (s, 3H), 3.59 (s, 3H), 2.83 (s, 3H), 2.59 (d,J=16.5 Hz, 1H), 2.42 (d, J=16.3 Hz, 1H), 2.09 (s, 1H), 1.66-1.57 (m,2H), 1.53 (s, 9H), 1.54-1.48 (m, 2H), 1.00 (s, 9H), 0.92 (s, 9H), 0.92(d, J=6.5 Hz, 3H) 0.86 (d, J=6.5 Hz, 3H), 0.17 (s, 6H), 0.13 (s, 3H),0.12 (s, 3H) ppm;

¹³C NMR (151 MHz, acetone-d₆): δ 172.3, 171.7, 171.3, 171.3, 171.1,170.8, 168.9, 168.0, 161.1, 159.9, 158.1, 156.9, 154.5, 153.0, 151.5,151.5, 141.5, 140.0, 138.4, 137.0, 136.9, 136.2, 135.7, 130.0, 129.3,129.3, 129.0, 128.3, 127.9, 127.6, 126.1, 125.4, 124.7, 124.1, 122.1,113.8, 106.5, 106.1, 105.4, 99.6, 80.3, 74.6, 74.0, 67.2, 64.3, 61.5,60.0, 57.5, 56.5, 56.2, 56.1, 55.7, 55.4, 55.2, 52.0, 38.1, 37.2, 28.9,28.6, 26.5, 26.3, 26.3, 25.7, 23.7, 23.3, 22.8, 19.1, 19.1, −4.4, −4.6,−4.8, −4.8.

HRMS (ESI-TOF, m/z): Calcd for C₈₁H₁₀₃Cl₂N₈O₁₉Si₂ [M+H]⁺ 1617.6249;found 1617.6248.

Compound 42

To a solution of S45 (600 mg, 0.37 mmol) in EtOH/EtOAc (4/1, 50 mL) wasadded Pd/C (240 mg, 5% Pd/C, 50% wetted powder); the resulting blacksuspension was stirred under a hydrogen atmosphere at room temperaturefor 12 h. The reaction mixture was then filtered through celite andwashed with EtOH/EtOAc (4:1, 150 mL). The filtrate was concentratedunder reduced pressure. The resulting residue was purified bypreparative reverse-phase HPLC (85%-100% CH₃CN/H₂O over 30 min, 100%CH₃CN for 30 min, both CH₃CN and H₂O containing 0.1% TFA) to afford 42(450 mg, 79%) as a TFA salt.

Note: The Boc group was found to cleaved during the purificationprocess.

Physical state: pale yellow film;

¹H NMR (600 MHz, MeOH-d₄): δ 8.68 (d, J=5.4 Hz, 1H), 7.60 (dd, J=8.4 Hz,2.4 Hz, 1H), 7.48 (br s, 1H), 7.42 (br s, 1H), 7.37 (d, J=8.4 Hz, 1H)7.40-7.35 (br m, 1H), 7.10 (d, J=9.0 Hz, 1H), 7.04-7.02 (m, 2H), 6.68(d, J=2.4 Hz, 1H), 6.58 (d, J=2.4 Hz, 1H), 6.39 (br s, 2H), 5.77 (d,J=1.2 Hz, 1H), 5.65 (br s, 1H), 5.46 (s, 1H), 5.37 (s, 1H), 5.30 (br s,1H), 4.80 (s, 1H), 4.60 (d, J=5.4 Hz, 1H), 4.23 (s, 3H), 4.10 (br s,1H), 3.93-3.90 (m, 1H), 3.87 (s, 3H), 3.73 (s, 3H), 3.67 (s, 3H), 2.83(s, 3H), 2.83-2.78 (m, 1H), 2.42 (dd, J=16.8, 5.4 Hz, 1H), 1.89-1.82 (m,1H), 1.79-1.74 (m, 2H), 0.98-0.93 (m, 24H), 0.15 (s, 3H), 0.15 (s, 3H),0.13 (s, 3H), 0.12 (s, 3H) ppm;

¹³C NMR (600 MHz, MeOH-d₄): δ 175.3, 174.0, 172.3, 171.9, 171.8, 171.4,170.4, 169.4, 169.2, 162.0, 160.4, 159.0, 155.2, 154.2, 153.3, 152.1,142.2, 140.0, 139.4, 137.3, 136.8, 135.4, 130.6, 129.2, 128.5, 128.5,128.0, 127.2, 126.1, 125.2, 124.9, 122.5, 114.1, 107.3, 106.7, 106.4,99.4, 74.9, 65.0, 62.5, 62.4, 61.1, 58.2, 56.6, 56.1, 56.0, 55.6, 52.4,40.8, 37.0, 33.2, 26.8, 26.5, 25.3, 23.7, 22.0, 19.7, 19.5, −4.3, −4.5,−4.7, −4.7 ppm;

¹⁹F NMR (376 MHz, MeOH-d₄): δ −77.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₆₉H₈₉Cl₂N₈O₁₇Si₂ [M+H]⁺ 1427.5256; found1427.5258.

Compound 43

To a solution of 42 (15.0 mg, 0.0097 mmol, 1.0 equiv.) in CH₃CN (1.5 mL)was added a solution of tris(dimethylamino)sulfoniumdifluorotrimethylsilicate (TASF) in DMF (120 μL, 1.0 M, 12.4 equiv.).The resulting mixture was stirred at room temperature for 1.5 h beforeit was concentrated to a final volume of ca. 0.1 mL under reducedpressure. This residue was purified by preparative reverse-phase HPLC(30%-45% CH₃CN/H₂O over 40 min, both CH₃CN and H₂O containing 0.1% TFA)to afford 43 (9.3 mg, 73%) as a TFA salt.

Physical state: white film;

¹H NMR (600 MHz, MeOH-d₄) δ 9.01 (d, J=6.4 Hz, 0.6H), 8.73 (d, J=5.8 Hz,0.4H), 7.86 (d, J=8.8 Hz, 1H), 7.75 (d, J=2.1 Hz, 1H), 7.65 (d, J=8.5Hz, 1H), 7.64 (d, J=2.1 Hz, 11H) 7.61 (ddd, J=8.5, 2.2, 0.9 Hz, 1H),7.21 (d, J=8.5 Hz, 1H), 7.09 (d, J=2.3 Hz, 1H), 6.85 (d, J=8.8 Hz, 1H),6.78 (d, J=8.2 Hz, 1H), 6.68 (d, J=2.3 Hz, 1H), 6.51 (d, J=2.2 Hz, 1H),6.13 (br s, 1H), 6.06 (s, 1H), 5.87 (s, 1H), 5.40 (dd, J=2.2, 1.0 Hz,1H), 5.37 (s, 1H), 5.27 (d, J=3.5 Hz, 1H), 4.78 (s, 1H), 4.65 (s, 1H),4.27 (dd, J=9.6, 1.9 Hz, 1H), 4.18 (s, 1H), 4.11 (s, 3H), 4.02 (t, J=7.2Hz, 1H), 3.86 (s, 3H), 3.66 (s, 3H), 3.63 (s, 3H), 3.03 (d, J=15.7 Hz,1H), 2.76 (s, 3H), 2.03 (dd, J=15.7, 10.4 Hz, 1H), 1.90 (dt, J=14.0, 7.2Hz, 1H), 1.69-1.57 (m, 2H), 0.88 (d, J=6.4 Hz, 3H), 0.85 (d, J=6.4 Hz,3H).

¹³C NMR (600 MHz, MeOH-d₄): δ 175.8, 174.6, 172.8, 171.7, 170.0, 169.9,169.4, 169.0, 161.9, 160.4, 158.7, 154.2, 153.0, 152.3, 151.1, 142.7,141.7, 138.1, 136.8, 136.7, 136.6, 130.2, 129.0, 129.0, 128.9, 128.5,127.6, 127.3, 125.3, 125.3, 124.8, 122.4, 113.8, 109.8, 106.7, 106.3,99.2, 74.3, 73.4, 63.9, 62.1, 61.9, 59.5, 58.5, 56.6, 56.3, 56.2, 56.0,55.2, 53.0, 52.9, 40.2, 38.7, 36.4, 33.0, 25.5, 23.2, 22.8 ppm;

¹⁹F NMR (376 MHz, MeOH-d₄): δ −76.9 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₅₇H₆₁Cl₂N₈O₁₇ [M+H]⁺ 1199.3526; found1199.3521.

Compound S46

To a suspension of 42 (45 mg, 0.029 mmol, 1.0 equiv.),N-hydroxyphthalimide (26 mg, 0.16 mmol, 5.5 equiv.), andN,N-dimethylpyridin-4-amine (0.4 mg, 0.0033 mmol, 0.11 equiv.) in CH₂Cl₂(0.5 mL) was added N,N′-diisopropylcarbodiimide (25 μL, 0.16 mmol, 5.5equiv.). The reaction mixture was stirred at room temperature for 1 hbefore AcOH (10 μL) was added. The resulting mixture was stirred foranother 2 h and was subjected to flash column chromatography directly(silica gel, column: d 1.6 cm×/7.5 cm, 3:2 EtOAc:hexanes (200 mL) to1:19 MeOH:CH₂Cl₂ (120 mL)). The combined fractions eluted withMeOH—CH₂Cl₂ were concentrated under reduced pressure, and the S46residue (31 mg) was used in next step without further purification.

Note:

(1) LC/MS indicated that the desired redox-active ester (S46) onlyeluted with MeOH/CH₂Cl₂. Nonpolar impurities, such as1,3-diisopropylurea, were found to elute with EtOAc:hexanes.(2) Additional amounts of DMAP or longer reaction time have deleteriouseffects on the reaction yield.(3) This redox-active ester (S46) was rather unstable and should be usedin next step within 3 h after purification. Alternatively, it can bestored at −20° C.

Compound S47

A screw-capped culture tube containing S46 (31 mg), MgBr₂.OEt₂ powder(38 mg, 0.15 mmol) was evacuated and backfilled with argon for threetimes. Suspension C (0.4 mL, NiCl₂.6H₂O/di-tBubipy in THF) was addednext and the mixture was stirred vigorously at room temperature for 15min (or sonicated until no granular MgBr₂.OEt₂ was observed). Theresulting suspension was cooled to 0° C., and the suspension of[B₂pin₂Me]Li in THF (0.55 mL) was added in one portion. After stirringfor 1 h, the reaction mixture was diluted with CH₂Cl₂ (5 mL), filteredthrough a short pad of silica gel and celite, washed with 5% MeOH/CH₂Cl₂(50 mL). The filtrate was concentrated under reduced pressure, and theresidue was subjected to flash column chromatography directly (silicagel, column: d 1.6 cm×17.5 cm, 1:1 EtOAc:hexanes (200 mL) to 1:19MeOH:CH₂Cl₂ (120 mL)). The MeOH—CH₂Cl₂ elution was concentrated underreduced pressure, and the S47 residue (16 mg) was used in next stepwithout further purification.

Note:

(1) The pinacol ester was found to hydrolyze during the reaction basedon LC/MS analysis.(2) LC/MS indicated that S47 only elutes with MeOH/CH₂Cl₂ based on LC/MSanalysis. Nonpolar impurities, such as B₂pin₂, were found to elute withEtOAc:hexanes.(3) Not all impurities can be removed through flash chromatography inthis step; instead the unpure materials were carried forward to the nextstep.

Compound 44

To a solution of S47 (16 mg) in CH₃CN (1.3 mL) was added a solution oftris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) in DMF(120 μL, 1.0 M). The mixture was stirred at room temperature for 1.5 hand was concentrated to a final volume of ca. 0.3 mL under reducedpressure. The residue was purified by preparative reverse-phase HPLC(20%-50% CH₃CN/H₂O over 30 min, both CH₃CN and H₂O containing 0.1% TFA)to afford 44 (4.1 mg, 11% over 3 steps) as a TFA salt.

Note: This compound was not stable in neat condition due to itspropensity toward polymerization. Therefore, the purified compound wasdissolved immediately. Solutions in MeOH were used for HRMS; solutionsin MeOH-d₄ were used for NMR study; solutions in DMSO were used forbiological studies.

Physical state: white film;

¹H NMR (600 MHz, MeOH-d₄): δ 9.05 (d, J=6.6 Hz, 1H), 7.65-7.58 (m, 4H),7.31 (d, J=9.0 Hz, 1H), 7.30 (d, J=9.6 Hz, 1H), 7.15 (dd, J=9.0 Hz, 1.8Hz, 1H), 6.97-6.91 (m, 2H), 6.81 (s, 1H), 6.52 (d, J=2.4 Hz, 1H), 5.81(d, J=5.4 Hz, 1H), 5.69 (s, 1H), 5.65 (s, 1H), 5.54 (s, 1H), 5.35 (d,J=3.6 Hz, 1H), 5.07 (br s, 1H), 5.04 (d, J=6.6 Hz, 1H), 4.43 (s, 1H),4.32 (d, J=5.4 Hz, 1H), 4.14 (s, 3H), 4.03 (t, J=7.2 Hz, 1H), 3.87 (s,3H), 3.68 (s, 3H), 3.65 (s, 3H), 2.96 (d, J=15.6, 1H), 2.77 (s, 3H),2.34 (dd, J=16.2 Hz, 9.0 Hz, 1H), 1.86-1.82 (m, 1H), 1.79-1.73 (m, 1H),1.71-1.86 (m, 1H), 1.01 (d, J=6.0 Hz, 3H), 0.98 (d, J=6.0 Hz, 3H) ppm;

¹¹B NMR (500 MHz, MeOH-d₄): δ −0.87 (s) ppm;

HRMS (ESI-TOF, m/z): Calcd for C₅₆H₆₂BCl₂N₈O₁₇ [M+H]⁺ 1199.3698; found1199.3698.

Experimental Procedure for Antibiotic Evaluation of 43, 44, Vancomycinand Vancomycin Aglycon.

Antibiotic susceptibilities were determined using the Clinical andLaboratory Standards Institute broth microdilution method (63). Briefly,antibiotics were prepared as 2-fold dilutions in 96-well platescontaining cation-adjusted Mueller-Hinton broth (S. aureus strains) orbrain-heart infusion broth (Enterococcus strains). Stock solutions ofantibiotics were made in dimethyl sulfoxide (DMSO). Wells wereinoculated from a fresh plate scrape diluted to a final concentration of5×10⁵ CFU/mL and incubated at 37° C. Growth observed visually at 20 h.All MICs are an average of at least three independent determinations.

Compd. S. aureus ^(a) MRSA^(b) E. faecium ^(c) E. faecalis ^(d) E.faecalis ^(e) vancomycin 0.5 0.5 >64 >64 16 vancomycin 1 1 >64 >64 32aglycon 43 2 2 >64 >64 8 44 16 16 >64 >64 16 ^(a) Staphylococcus aureus(ATCC 25923) ^(b) Staphylococcus aureus (methicillin resistant, ATCC43300) ^(c) Enterococcus faecium (Van A, ATCC BAA-2317) ^(d)Enterococcus faecalis (VanA, BM4166) ^(e) Enterococcus faecalis (VanB,ATCC 51299) Note: compound 44 was not very stable in H₂O at 37° C. underair. Under such conditions, ca. 20% of 44 was found to have decomposedafter 24 h as indicated by LC/MS analysis (254 nM UV detector).

Probing the Stereoselectivity on Peptide Substrates Compound S48

1,3-dioxoisoindolin-2-yl (tert-butoxycarbonyl)-L-alanyl-L-valinate (S48)

N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC, 422mg, 2.2 mmol, 1.1 equiv.) was added into a solution ofBoc-L-Ala-L-Val-OH (2.0 mmol, 1.0 equiv.) and NHPI (359 mg, 2.2 mmol,1.1 equiv.) in CH₂Cl₂ (30 mL) at −10° C. After stirring for 1 h at roomtemperature, the mixture was washed with water and the aqueous phase wasextracted with CH₂Cl₂ for three times. The combined organic phases weredried over anhydrous Na₂SO₄ and concentrated in vacuo. Purification byflash column chromatography (silica gel, 3:7 EtOAc:hexanes to EtOAc)afforded S48 (591 mg, 62%).

Physical state: white foam;

R_(f)=0.36 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.88 (dd, J=5.5, 3.1 Hz, 2H), 7.79 (dd,J=5.5, 3.1 Hz, 2H), 6.93-6.79 (br, 1H), 5.02-4.88 (m, 2H), 4.28-4.14(br, s, 1H), 2.48-2.32 (m, 1H), 1.44 (s, 9H), 1.38 (d, J=7.0 Hz, 3H),1.10 (d, J=6.9 Hz, 3H), 1.08 (d, J=6.9 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.6, 168.4, 161.6, 155.9, 135.0, 129.0,124.2, 80.5, 55.6, 50.0, 31.8, 28.4, 18.9, 17.5 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₁H₂₈N₃O₇ [M+H]⁺ 434.1922; found434.1930.

Compound 45

tert-butyl((2S)-1-((2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)prop-yl)amino)-1-oxopropan-2-yl)carbamate(45)

On 0.2 mmol scale, General Procedure C was followed with suspension C(NiCl₂.6H₂O/di-tBubipy in THF). Flash column chromatography (silica gel,3:7 EtOAc:hexanes) afforded 45 as a mixture of inseparable diastereomers(50 mg, dr=1:1, 67%)

Physical state: colorless oil;

R_(f)=0.22 (silica gel, 3:7 EtOAc:hexanes);

¹H NMR (600 MHz, C₆D6): δ 6.77 (s, 1H), 6.73 (s, 1H), 5.56 (s, 1H), 5.37(s, 1H), 4.23 (s, 1H), 4.11 (s, 1H), 3.05 (s, 2H), 2.10-2.04 (m, 2H),1.41 (s, 9H), 1.40 (s, 9H), 1.25-0.92 (m, 42H) ppm;

¹³C NMR (151 MHz, C₆D6): δ 174.7, 174.2, 156.0, 155.9, 82.8, 82.6, 79.4,74.7, 49.1, 49.0, 37.0, 30.3, 28.4, 25.3, 25.3, 25.2, 25.0, 20.7, 20.7,20.0, 19.9, 17.9, 17.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₃₆BN₂O₅[M+H]⁺ 371.2712; found371.2710.

On a 2.0 mmol scale, General Procedure A was followed withBoc-L-Val-L-Val-OH (S49). Purification by flash column chromatography(silica gel, 1:3 EtOAc:hexanes) afforded S50a (187 mg, 20%) and S50b(395 mg, 43%).

Compound S50a

1,3-dioxoisoindolin-2-yl (tert-butoxycarbonyl)-L-valyl-L-valinate (S50a)

Physical state: white foam;

R_(f)=0.40 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.90-7.88 (m, 2H), 7.81-7.79 (m, 2H), 6.48(br d, J=8.8 Hz, 1H), 5.09 (br d, J=8.4 Hz, 1H), 4.98 (dd, J=8.8, 5.1Hz, 1H), 3.91 (dd, J=8.7, 6.8 Hz, 1H), 2.43-2.38 (m, 1H), 2.14 (br s,1H), 1.43 (s, 9H), 1.11 (t, J=6.3 Hz, 6H), 0.97 (dd, J=16.5, 6.8 Hz, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 171.9, 168.4, 161.6, 156.1, 135.0, 129.0,124.2, 80.2, 60.4, 55.6, 31.7, 30.6, 28.4, 19.4, 18.9, 18.2, 17.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₂₄N₃O₅ [M-Boc+H]⁺ 362.1710; found362.1705;

[α]D²⁰=−31.8 (c 0.96, CHCl₃).

Compound S50b

1,3-dioxoisoindolin-2-yl (tert-butoxycarbonyl)-L-valyl-L-valinate (S50b)

Physical state: white foam;

R_(f)=0.4 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.87-7.85 (m, 2H), 7.79-7.77 (m, 2H), 6.60(br d, J=8.8 Hz, 1H), 5.15 (d, J=8.9 Hz, 1H), 4.96 (dd, J=8.8, 5.2 Hz,1H), 3.92 (dd, J=8.8, 6.8 Hz, 1H), 2.41-2.36 (m, 1H), 2.10 (br s, 1H),1.42 (s, 9H), 1.09 (dd, J=6.9, 4.6 Hz, 6H), 0.97 (d, J=6.8 Hz, 3H), 0.94(d, J=6.8 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.0, 168.4, 161.6, 156.1, 134.9, 128.9,124.1, 80.1, 60.3, 55.6, 31.6, 30.6, 28.4, 19.4, 18.9, 18.2, 17.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₂₄N₃O₅ [M-Boc+H]⁺ 362.1710; found362.1714;

[α]D²⁰=−31.2 (c 1.0, CHCl₃).

Compound 46

tert-butyl((S)-3-methyl-1-(((S)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-lan-2-yl)propyl)amino)-1-oxobutan-2-yl)carbamate(46) From S50a:

On 0.2 mmol scale, General Procedure C was followed with suspension C(NiCl₂.6H₂O/di-tBubipy in THF) from S50a (1.0 equiv. of MgBr₂.Et₂O wasused in this case). Purification by flash column chromatography (silicagel, 1:3 EtOAc:hexanes) afforded 46 as a mixture of inseparablediastereomers (37.1 mg, d.r.=1.7:1, 47%)

From S50b:

On 0.2 mmol scale, General Procedure C was followed with suspension C(NiCl₂.6H₂O/di-tBubipy in THF) from S50b (1.0 equiv. of MgBr₂.Et₂O wasused in this case). Purification by flash column chromatography (silicagel, 1:3 EtOAc: hexanes) afforded 46 as a mixture of inseparablediastereomers (36.5 mg, d.r.=1.7:1, 46%).

Physical state: colorless oil;

R_(f)=0.30 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 6.30 (br d, J=5.5 Hz, 0.78H), 6.22 (br s,0.22H), 5.10 (br d, J=8.7 Hz, 1H), 3.92-3.86 (m, 1H), 3.03 (br s, 1H),2.10 (br s, 1H), 1.96-1.90 (m, 1H), 1.42 (s, 9H), 1.28-1.16 (m, 12H),0.95 (d, J=6.7 Hz, 3H), 0.93 (d, J=6.7 Hz, 3H), 0.92 (d, J=6.7 Hz, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.48 (minor), 172.46, 155.92, 83.37,79.91, 59.57 (minor), 59.25, 44.96 (br), 31.10, 31.02 (minor), 30.01,29.91 (minor), 28.51, 28.44, 25.18, 25.12, 25.10 (minor), 25.03 (minor),24.97, 20.42, 20.37 (minor), 20.12, 20.03, 19.35, 19.21 (minor), 18.13(minor), 17.90 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₀H₄₀BN₂O₅[M+H]⁺ 399.3025; found399.3028.

Compound S51

tert-butyl(R)-2-(((S)-1-((1,3-dioxoisoindolin-2-yl)oxy)-3-methyl-1-oxobutan-2-yl)carbamoyl)pyrrolidine-1-carboxylate (S51)

On 1.0 mmol scale (based on Boc-L-Pro-L-Leu-OH), the same procedure asin the synthesis of S48 was used. Purification by flash columnchromatography (silica gel, 1:2 EtOAc:hexanes) afforded S51 (308 mg,67%).

Physical state: white foam;

R_(f)=0.4 (silica gel, 1:1 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): δ 7.88-7.85 (m, 2H), 7.87 (br s, 0.6H),7.79-7.77 (m, 2H), 6.63 (s, 0.4H), 4.99-4.88 (m, 1H), 4.37-4.30 (m, 1H),3.61-3.21 (m, 2H), 2.47 (br s, 0.4H), 2.43-2.37 (m, 1H), 2.16 (br s,0.6H), 2.03-1.76 (m, 3H), 1.51-1.39 (m, 9H), 1.12-1.03 (m, 6H); (complexspectrum was observed due to mixture of rotamers);

¹³C NMR (151 MHz, CDCl₃): δ 172.7, 172.0, 168.4, 161.6, 156.3, 154.9,140.9, 137.2, 134.9, 130.1, 129.0, 124.1, 115.6, 110.4, 81.4, 80.7,61.3, 59.5, 55.7, 55.1, 47.0, 31.5, 28.5, 27.1, 24.8, 19.0, 17.5;(complex spectrum was observed due to mixture of rotamers);

HRMS (ESI-TOF, m/z): Calcd for C₁₈H₂₂N₃O₅ [M-Boc+H]⁺ 360.1554; found360.1554.

Compound 47

tert-butyl2-(((S)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl)carbamoyl)pyrrolidine-1-carboxylate (47)

On 0.28 mmol scale, General Procedure C was followed with S51 andsuspension C (NiCl₂. 6H₂O/di-tBubipy in THF). Purification by flashcolumn chromatography (silica gel, 2:1 EtOAc:hexanes) afforded 47 as amixture of diastereomers (70.5 mg, d.r.=2.6:1, 63%). Diastereomericratio was determined by ¹H NMR and NOESY in DMSO-d₆ at 65° C.

Physical state: colorless oil;

R_(f)=0.30 (silica gel, 2:1 EtOAc:hexanes);

¹H NMR (500 MHz, DMSO-d₆): δ 8.37 (s, 0.72H), 8.28 (s, 0.28H), 4.25 (dd,J=8.5, 2.8 Hz, 1H), 3.44-3.35 (m, 1H), 3.34-3.27 (m, 1H), 2.46 (t, J=5.3Hz, 0.28H), 2.40 (t, J=4.7 Hz, 0.72H), 2.19-2.05 (m, 1H), 1.89-1.74 (m,4H), 1.39 (s, 9H), 1.13 (s, 3.36H), 1.12 (s, 8.64H), 0.93-0.85 (m, 6H)ppm;

¹³C NMR (126 MHz, DMSO-d₆): δ 174.9, 153.0, 80.6 (minor), 80.4, 78.5,57.5 (minor), 57.3, 46.2, 28.9 (minor), 28.7, 27.8, 27.7, 24.9 (minor),24.8, 24.7, 20.1, 20.0 (minor), 19.2 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₀H₃₈BN₂O₅[M+H]⁺ 397.2868; found397.2864.

Stereoselective Synthesis of Bortezomib (Velcade)

Compound S56

1,3-dioxoisoindolin-2-yl (tert-butoxycarbonyl)-L-phenylalanylleucinate(S53)

On 3.0 mmol scale, General Procedure A was followed withBoc-L-Phe-L-Leu-OH (64) (S62). Purification by flash columnchromatography (deactivated silica gel, 1:5.6 EtOAc:hexanes) affordedS53 as a mixture of inseparable diastereomers (1.42 g, d.r.=3:2, 90%).Diastereomeric ratio was determined by ¹H NMR and NOESY.

Physical state: White foam;

R_(f)=0.50 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, MeOH-d4): Minor isomer: δ 7.94-7.89 (m, 4H), 7.29-7.15(m, 5H), 4.78 (dd, J=9.5 Hz, 5.8 Hz, 1H), 4.39-4.35 (m, 1H), 3.05 (dd,J=13.7 Hz, 7.2 Hz, 1H), 2.90 (dd, J=13.6 Hz, 8.1 Hz, 1H), 1.76-1.70 (m,2H), 1.54-1.50 (m, 1H), 1.38 (s, 9H), 0.94 (d, J=6.6 Hz, 3H), 0.89 (d,J=6.6 Hz, 3H) ppm; Major isomer: δ 7.94-7.89 (m, 4H), 7.29-7.15 (m, 5H),4.92 (dd, J=9.6 Hz, 6.0 Hz, 1H), 4.39-4.35 (m, 1H), 3.13 (dd, J=14.4 Hz,5.4 Hz, 1H), 2.84 (dd, J=13.8 Hz, 9.0 Hz, 1H), 1.89-1.83 (m, 3H), 1.37(s, 9H), 1.02 (d, J=6.0 Hz, 3H), 0.99 (d, J=6.0 Hz, 3H) ppm;

¹³C NMR (151 MHz, MeOH-d4): Minor isomer: δ 174.4, 170.4, 163.1, 157.3,138.3, 136.3, 135.5, 130.4, 130.1, 129.5, 127.7, 124.9, 124.0, 80.7,57.4, 50.2, 41.2, 39.6, 28.6, 28.4, 25.7, 25.5, 23.2, 21.7 ppm; Majorisomer: δ 174.6, 170.4, 163.1, 157.6, 138.4, 136.4, 135.5, 130.4, 130.1,129.4, 127.6, 124.9, 124.0, 80.6, 57.1, 50.2, 41.5, 39.1, 28.6, 28.4,25.7, 25.5, 23.2, 21.8 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₃H₂₆N₃O₅ [M-Boc+H]⁺ 424.1867; found424.1871.

Compound 48

tert-butyl((S)-1-(((R)-3-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)butyl)amino)-1-oxo-3-phenylpropan-2-yl)carbamate (48)

On 0.6 mmol scale, General Procedure C was followed with suspension C(NiCl₂. 6H₂O/di-tBubipy in THF) and S53. The reaction was started from□15° C. and warmed to room temperature over 3 h. Flash columnchromatography (silica gel, 1:9 EtOAc:hexanes to 1:4 EtOAc:hexanes)afforded 48, which was dissolved in hexanes and filtered through celite.The filtrate was concentrated in vacuo to afford 48 as a mixture ofinseparable diastereomers (151 mg, d.r.=5.1:1, 55%).

Physical state: Pale yellow oil;

R_(f)=0.50 (silica gel, 2:3 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃): Major isomer: δ 7.31-7.26 (m, 2H), 7.24-7.21(m, 3H), 6.19 (br s, 1H), 5.00 (br s, 1H), 4.35 (q, J=7.3 Hz, 1H),3.10-3.02 (m, 2H), 2.98 (ddd, J=8.8 Hz, 6.3 Hz, 4.4 Hz, 1H), 1.49-1.42(m, 1H), 1.39 (s, 9H), 1.37-1.35 (m, 2H), 1.24 (s, 6H), 1.23 (s, 6H),0.86 (d, J=6.6 Hz, 3H), 0.84 (d, J=6.6 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): Major isomer: δ 172.6, 155.5, 134.4, 129.6,128.8, 127.1, 83.0, 80.3, 54.8, 39.9, 38.3, 28.4, 25.6, 25.1, 25.0,23.3, 22.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₅H₄₂BN₂O₅[M+H]⁺ 461.3181; found461.3179.

Compound 49

(3-methyl-1-((S)-3-phenyl-2-(pyrazine-2-carboxamido)propanamido)butyl)boronicacid (49)

Bortezomib (49) was synthesized from 48 using the literature procedure(19) with slight modifications.

Boc Deprotection:

To a screw-capped culture tube charged with 48 (151 mg, 0.33 mmol) wasadded HCl in EtOAc (14 wt %) at 0° C., and the reaction mixture wasstirred at 0° C. for 3 h and room temperature for an additional 1 h. Thereaction mixture was concentrated to dryness and the resulting solid waswashed with hexanes. The desired product was afforded as a white solidand was used in next step without further purification.

Esterification:

CH₂Cl₂ (1.2 mL, 0.5 M) was added to a screw-capped culture tubecontaining the hydrochloride salt obtained from the previous step. Themixture was cooled to 0° C. Diisopropylethylamine (0.15 mL, 0.86 mmol)was added dropwise, and the reaction mixture was stirred for 5 min.2-Pyrazine carboxylic acid (56 mg, 0.45 mmol) was then added to thesolution in one portion.O-(Benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate(TBTU, 118 mg, 0.37 mmol) was then added to the reaction mixture whichwas stirred at 0° C. for 2 h and room temperature for additional 1 h.The reaction mixture was then concentrated in vacuo. The crude residuewas dissolved in EtOAc (10 mL) and transferred to a separatory funnel.The organic layer was washed with deionic H₂O (2×10 mL), 1% phosphoricacid (2×10 mL), 2% K₂CO₃ (2×10 mL), and brine (2×10 mL) successively.Each aqueous layer was back-extracted with EtOAc (2×10 mL). The combinedorganic layers were dried over anhydrous Na₂SO₄, filtered andconcentrated in vacuo. The resulting pale yellow foam was carried on tothe next step without further purification.

Boronate Ester Exchange:

Pentane (0.8 mL) and MeOH (0.8 mL) were added to a screw-capped culturetube containing the pinacol boronate obtained from the previous step.2-Methylpropaneboronic acid (125 mg, 1.2 mmol) was then added to thesolution. 1 N aq. HCl (0.6 mL) was added to the reaction mixture, andthe resulting biphasic solution was stirred vigorously for 16 h.Stirring was then stopped and the biphasic mixture was allowed toseparate. The aqueous layer was washed with pentane (2×10 mL) and wasthen concentrated in vacuo. The resulting film was partitioned betweenCH₂Cl₂ and 1 N aq. NaOH (10 mL). The aqueous layer was washed withCH₂Cl₂ (3×10 mL) and the organic phase was back-extracted with 1 N aq.NaOH (2×10 mL). 1 N aq. HCl was added to the combined aqueous layersuntil the pH=6 when the desired product was extracted into the organiclayer with CH₂Cl₂ (3×10 mL). The combined organic phase was dried overanhydrous Na₂SO₄, filtered, and concentrated in vacuo. The resultingresidue was dissolved in EtOAc (2 mL), and the solution was subsequentlyconcentrated in vacuo. To the residue was then added hexanes (2 mL), andthe suspension was concentrated in vacuo to afford the product 49 (64mg, d.r.=5.1:1, 51% over 3 steps).

Physical state: white solid;

¹H NMR (600 MHz, CD₃CN:D₂O=4:1): Major isomer: δ 9.10 (d, J=1.8 Hz, 1H),8.74 (d, J=2.4 Hz, 1H)), 8.61 (dd, J=2.4 Hz, 1.8 Hz, 1H), 7.26-7.22 (m,4H), 7.20-7.17 (m, 1H), 4.78 (dd, J=8.4 Hz, 6.0 Hz, 1H), 3.19 (dd,J=13.8 Hz, 6.0 Hz, 1H), 3.07 (dd, J=13.8 Hz, 8.2 Hz, 1H), 2.93 (dd,J=10.2 Hz, 5.4 Hz, 1H), 1.44-1.33 (m, 2H), 1.26-1.21 (m, 1H), 0.80 (d,J=6.6 Hz, 3H), 0.78 (d, J=6.6 Hz, 3H) ppm;

¹³C NMR (151 MHz, CD₃CN:D₂O=4:1): Major isomer: 172.4, 164.5, 148.7,145.0, 144.7, 144.4, 137.7, 130.4, 129.5, 127.8, 54.9, 40.2, 40.2 (brs), 38.5, 25.9, 23.6, 22.0 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₉H₂₄BN₄O₃[M−H₂O+H]⁺ 367.1936; found367.1950.

Synthesis of Elastase Inhibitor 50

Compound 50a

(methoxycarbonyl)-L-valyl-L-prolyl-L-valine (50a)

Cbz deprotection: A 100 mL flask equipped with a stirrer bar was chargedwith Z-L-Pro-L-Val-OtBu (65) (S54, 2.55 g, 6.3 mmol), 10% Pd/C (128 mg,5 wt %), and MeOH (30 mL). The flask was then evacuated and backfilledwith H₂ from a balloon for three times. The mixture was stirred at roomtemperature for 6 h and was filtered through a short pad of celite whichwas then rinsed with MeOH (10 mL). The filtrate was concentrated invacuo to give the corresponding amine as colorless oil.

Amide Bond Formation:

The aforementioned amine was treated successively with S55 (1.1 g, 6.3mmol, 1.0 equiv.), HOBt H₂O (96 mg, 0.07 mmol, 0.11 equiv.), and CH₂Cl₂(25 mL). The resulting solution was cooled to 0° C. before DCC (1.43 g,6.9 mmol, 1.1 equiv.) was added. The reaction mixture was allowed tostir at 0° C. for 30 min and then at room temperature overnight. Thereaction mixture was filtrered through a pad a celite; the filtrate wasredissolved in EtOAc and washed with 0.1 N aq. HCl, 0.1 M aq.NH₄OH, andbrine successively. The organic layer was dried over anhydrous Na₂SO₄and concentrated in vacuo to give S56 (2.2 g) as colorless oil, whichwas used in the next step without further purification.

tBu Deprotection:

In a 25 mL flask equipped with a stirrer bar, S56 (428 mg, 1.0 mmol) wasdissolved in CH₂Cl₂ (3 mL). TFA (3 mL) was added and the resultingsolution was allowed to stir at room temperature for 5 h. After thevolatiles were removed in vacuo, the crude mixture was purified by flashcolumn chromatography (silica gel, 2:1 EtOAc:hexanes) furnished 50a (359mg, 80% over 3 steps).

Physical state: white foam;

R_(f)=0.35 (silica gel, 1:2 hexanes: EtOAc);

¹H NMR (600 MHz, CDCl₃): δ 7.43 (br d, J=8.4 Hz, 2H), 6.17 (d, J=9.0 Hz,1H), 4.64 (dd, J=7.8 Hz, 3.0 Hz, 1H), 4.48 (dd, J=8.4 Hz, 4.0 Hz, 1H),4.29 (t, J=8.4 Hz, 1H), 3.84 (dd, J=16.8 Hz, 8.4 Hz, 1H), 3.69-3.63 (m,4H), 2.33-2.29 (m, 1H), 2.20-2.10 (m, 2H), 2.03-1.92 (m, 3H), 0.97 (d,J=6.6 Hz, 3H), 0.95 (d, J=6.6 Hz, 3H), 0.91 (d, J=7.2 Hz, 3H), 0.89 (d,J=7.2 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 174.5, 173.5, 171.1, 157.8, 60.6, 58.1,57.8, 52.5, 48.3, 31.4, 31.2, 27.7, 25.2, 19.4, 19.0, 18.1, 17.8 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₇H₃₀N₃O₆ [M+H]⁺ 372.2129; found372.2126;

[α]D²⁰=−62.9 (c 0.79, CHCl₃)

Compound S57

1,3-dioxoisoindolin-2-yl (methoxycarbonyl)-L-valyl-L-prolylvalinate(S57)

On 2.34 mmol scale, General Procedure A was followed with(methoxycarbonyl)-L-valyl-L-prolyl-L-valine. Purification by flashcolumn chromatography (silica gel, 1:1 EtOAc:hexanes) furnished S57 (640mg, 53%).

Physical state: white foam;

R_(f)=0.40 (silica gel, 1:2 hexanes: EtOAc);

¹H NMR (600 MHz, CDCl₃) δ 7.88-7.84 (m, 2H), 7.78-7.75 (m, 2H), 7.50 (d,J=8.4 Hz, 1H), 5.61 (d, J=9.2 Hz, 1H), 4.84 (dd, J=8.5, 5.0 Hz, 1H),4.61 (dd, J=8.1, 3.0 Hz, 1H), 4.29 (dd, J=9.3, 6.9 Hz, 1H), 3.79-3.72(m, 1H), 3.63 (s, 3H), 3.64-3.61 (m, 1H), 2.41-2.30 (m, 2H), 2.17 (dt,J=12.3, 9.1 Hz, 1H), 2.01-1.96 (m, 2H), 1.95-1.89 (m, 1H), 1.07 (d,J=7.2 Hz, 3H), 1.06 (d, J=6.6 Hz, 3H), 0.97 (d, J=6.7 Hz, 3H), 0.93 (d,J=6.7 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃) δ 172.5, 171.2, 168.4, 161.7, 157.3, 134.9,129.0, 124.1, 60.0, 57.7, 56.0, 52.4, 48.0, 31.6, 31.4, 27.4, 25.3,19.5, 18.8, 17.8, 17.7 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₅H₃₃N₄O₈ [M+H]⁺ 517.2293; found517.2289;

[α]D²⁰=−61.0 (c 1.0, CHCl₃).

Compound S58

methyl((S)-3-methyl-1-((S)-2-(((R)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxab-orolan-2-yl)propyl)carbamoyl)pyrrolidin-1-yl)-1-oxobutan-2yl)-carbamate(S58)

On 0.33 mmol scale, General Procedure C was followed with suspension C(NiCl₂.6H₂O/di-tBubipy in THF). MgBr₂.Et₂O (1.0 equiv.) was used in thiscase. Purification by flash column chromatography (silica gel, 2:3EtOAc:hexanes to 20:1 CH₂Cl₂:MeOH) furnished S58 (72 mg, 48%) asslightly yellow oil.

Compound 50

((R)-1-((S)-1-((methoxycarbonyl)-L-valyl)pyrrolidine-2-carboxamido)-2-methylpropyl)boronicacid (50)

Aminoboronate ester S58 (24 mg, 0.053 mmol) was dissolved in CH₂Cl₂ (2mL) under argon; the solution was cooled to −78° C. with a dryice/acetone bath when BCl₃ (0.16 mL, 1.0 M in CH₂Cl₂, 3.0 equiv.) wasadded dropwise, after which the mixture was stirred for 1 h at −78° C.The reaction was then allowed to warm up to room temperature, and thevolatiles were removed in vacuo. Anhydrous methanol (4 mL) was added andthe resulting mixture was stirred for 10 minutes prior to concentrationin vacuo. The resulting residue was treated with methanol (4 mL) for 10minutes and was concentrated in vacuo. This process was repeated forthree times. The resulting crude product was then purified bypreparative reverse-phase HPLC (10-40% CH₃CN/H₂O over 25 min, both CH₃CNand H₂O containing 0.1% TFA) and lyophilized to afford 50 as a whitefloppy powder (15.0 mg, 76%).

Physical state: white powder;

¹H NMR (600 MHz, MeOH-d₄): δ 4.61 (dd, J=8.4 Hz, 6.0 Hz, 1H), 4.17 (d,J=7.8 Hz, 1H), 3.97-3.93 (m, 1H), 3.75-3.71 (m, 1H), 3.64 (s, 3H),2.33-2.24 (m, 2H), 2.19-2.13 (m, 1H), 2.08-1.98 (m, 3H), 1.80-1.74 (m,1H), 1.05 (d, J=6.6 Hz, 3H), 1.00 (d, J=6.6 Hz, 3H), 0.96 (d, J=6.6 Hz,3H), 0.92 (d, J=6.6 Hz, 3H) ppm;

¹³C NMR (151 MHz, MeOH-d₄): δ 179.3, 173.5, 159.4, 59.7, 57.9, 52.7,31.7, 31.0, 29.8, 26.2, 21.4, 21.2, 19.6, 18.8 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₁₆H₂₉BN₃O₅[M−H₂O+H]⁺ 354.2195; found354.2189;

[α]D²⁰=−81.1 (c 0.44, MeOH).

Synthesis of Elastase Inhibitors mCBK320 (51) and mCBK323(52)

Compound S60

(tert-butoxycarbonyl)-L-valyl-L-prolyl-L-valine (S60)

Cbz Deprotection:

A 100 mL flask equipped with a stirrer bar was charged withZ-L-Pro-L-Val-OMe (66) (S59, 1.95 g, 5.4 mmol), 10% Pd/C (98 mg, 5 wt%), and MeOH (25 mL). This flask was then evacuated and backfilled withH₂ from a balloon for three times. The reaction mixture was stirred atroom temperature for 6 h and was filtered through a thin pad of celitewhich was then rinsed with MeOH (10 mL). The filtrate was concentratedin vacuo to give the corresponding amine as colorless oil.

Amide Bond Formation:

The aforementioned amine was treated sequentially with Boc-L-Valine(1.17 g, 5.4 mmol, 1.0 equiv.), HOBt.H₂O (83 mg, 0.61 mmol, 0.11equiv.), and CH₂Cl₂ (25 mL). The resulting solution was cooled to 0° C.before DCC (1.23 g, 6.0 mmol, 1.1 equiv.) was added. The reactionmixture was allowed to stir at 0° C. for 30 min and then at roomtemperature overnight. The resulting mixture was filtered through a padof celite; the filtrate was concentrated in vacuo, redissolved in EtOAc,and washed with 0.1N aq. HCl, 0.1 M aq. NH₄OH, and brine successively.The organic layer was dried over anhydrous Na₂SO₄, concentrated invacuo, and purified by flash column chromatography (silica gel, 2:1EtOAc:hexanes) to give Boc-L-Val-L-Pro-L-Val-OMe (1.32 g) as a colorlessoil.

Hydrolysis of Ester:

A 25 mL flask equipped with a stirrer bar was charged withBoc-L-Val-L-Pro-L-Val-OMe (1.32 g) and THF (3 mL). LiOH (4 mL, 1 Maqueous solution) was added and the resulting solution was allowed tostir vigorously at room temperature for 12 h. 1 N HCl was added to thereaction mixture until pH=2-3 and the mixture was extracted with EtOAc.The combined organic layers were dried over anhydrous Na₂SO₄ andconcentrated in vacuo to give S60 (1.24 g, 53% over 3 steps) as a whitefoam, which was used in the next step without further purification.

Compound S61

1,3-dioxoisoindolin-2-yl (tert-butoxycarbonyl)-L-valyl-L-prolylvalinate(S61)

On 3.0 mmol scale, General Procedure A was followed withBoc-L-valyl-L-prolyl-L-valine (S60). Purification by flash columnchromatography (silica gel, 1:1 EtOAc:hexanes) furnished S61 (920 mg,55%).

Physical state: white foam;

R_(f)=0.50 (silica gel, 1:2 hexane: EtOAc);

¹H NMR (600 MHz, CDCl₃): δ 7.88-7.85 (m, 2H), 7.79-7.76 (m, 2H), 7.50(d, J=8.4 Hz, 1H), 5.28 (d, J=9.6 Hz, 1H), 4.84 (dd, J=8.4, 4.8 Hz, 1H),4.62 (dd, J=7.8, 3.0 Hz, 1H), 4.28 (dd, J=9.6, 6.6 Hz, 1H), 3.71-3.77(m, 1H), 3.60 (dt, J=8.4, 3.6 Hz, 1H), 2.43-2.39 (m, 1H), 2.37-2.31 (m,1H), 2.11-2.19 (m, 1H), 1.88-2.02 (m, 3H), 1.41 (s, 9H), 1.08 (d, J=6.6Hz, 3H), 1.07 (d, J=6.6 Hz, 3H), 0.98 (d, J=7.2 Hz, 3H), 0.92 (d, J=7.2Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.9, 171.1, 168.3, 161.7, 156.0, 134.9,129.0, 124.1, 79.7, 60.0, 57.0, 56.1, 47.9, 31.6, 31.6, 28.5, 27.1,25.4, 19.7, 18.9, 17.8, 17.6 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₈H₃₉N₄O₈ [M+H]⁺ 559.2762; found559.2757.

[α]D²⁰=−86.2 (c 1.0, CHCl₃).

Compound S62

tert-butyl((S)-3-methyl-1-((S)-2-(((R)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-diox-aborolan-2-yl)propyl)carbamoyl)pyrrolidin-1-yl)-1-oxobutan-2-yl)carbamate(S62)

On 1.1 mmol scale, General Procedure C was followed with S61 andsuspension C (NiCl₂.6H₂O/di-tBubipy in THF), 1.0 equiv. of MgBr₂.Et₂Owas used in this case. Flash column chromatography (silica gel, 2:3EtOAc:hexanes to 3:1 EtOAc:hexanes) furnished S62 (257 mg, 47%) as aslightly yellow oil.

Physical state: slight yellow oil;

R_(f)=0.65 (silica gel, 1:2 hexanes: EtOAc);

¹H NMR (600 MHz, CDCl₃): δ 7.08 (br s, 1H), 5.22 (d, J=9.3 Hz, 1H), 4.66(dd, J=8.2, 2.6 Hz, 1H), 4.28 (dd, J=9.3, 6.0 Hz, 1H), 3.70 (q, J=8.7Hz, 1H), 3.56 (ddd, J=9.7, 8.1, 3.7 Hz, 1H), 2.97-2.86 (m, 1H),2.41-2.38 (m, 1H), 2.19-2.11 (m, 1H), 2.01-1.94 (m, 2H), 1.94-1.80 (m,2H), 1.43 (s, 9H), 1.25 (d, J=5.4 Hz, 12H), 0.97 (d, J=6.8 Hz, 3H), 0.95(d, J=6.8 Hz, 3H), 0.93 (d, J=6.8 Hz, 3H), 0.91 (d, J=6.7 Hz, 3H) ppm;

¹³C NMR (151 MHz, CDCl₃): δ 172.8, 171.8, 156.0, 83.3, 79.8, 59.0, 56.9,47.7, 31.6, 29.8, 28.5, 27.0, 25.3, 25.2, 25.1, 20.6, 20.3, 19.7, 17.5ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₅H₄₇BN₃O₆[M+H]⁺ 496.3552; found496.3550.

[α]D²⁰=−73.6 (c 1.0, CHCl₃).

Compound 51

(1-((S)-1-((4-(((4-chlorophenyl)sulfonyl)carbamoyl)benzoyl)-L-valyl)pyrrolidine-2-carboxamido)-2-methylpropyl)boronicacid (51)

Boc deprotection: In a culture tube equipped with a stir bar, S62 (55mg, 0.11 mmol) was dissolved in CH₂Cl₂ (1 mL). TFA (1 mL) was added at0° C. and the resulting solution was allowed to stir at 0° C. for 2 h.The volatiles were removed in vacuo using a rotary evaporator (waterbath temperature <25° C.), and the residue was used in next step withoutpurification.

Esterification:

Benzoic acid S63 (45 mg, 0.13 mmol, 1.2 equiv.) and PyBOP (69 mg, 0.13mmol, 1.2 equiv.) were then added and the mixture was dissolved in DMF(2.0 mL). N-methyl morpholine (49 μL, 0.45 mmol, 4.0 equiv.) was addedand the reaction was allowed to stir at room temperature for 3 h. Themixture was then diluted with EtOAc, washed with brine, dried overanhydrous Na₂SO₄, concentrated in vacuo, and purified by flash columnchromatography (silica gel, 10:1 CH₂Cl₂:MeOH) to give the pinacolboronate of 51 (69 mg) contaminated with some tripyrrolidinophosphineoxide. This mixture was used in the next step without furtherpurification.

Boronate Ester Exchange:

In a culture tube equipped with a stir bar, the aforementioned mixture(53 mg) and PhB(OH)₂ (14 mg) was dissolved in Et₂O (3 mL). 2 N HCl (3mL) was added and the resulting biphasic mixture was allowed to stirvigorously at room temperature for 36 h when it was extracted with EtOAc(5 mL×3). The combined organic layers were dried over anhydrous Na₂SO₄,concentrated in vacuo. The resulting residue was purified by preparativereverse-phase HPLC (20-80% CH₃CN/H₂O over 35 min, both CH₃CN and H₂Ocontaining 0.1% TFA) and lyophilized to afford 51 (14.0 mg, 26% for 3steps).

Physical state: white powder;

¹H NMR (600 MHz, MeOH-d₄): δ 8.10 (d, J=8.4 Hz, 2H), 7.94-7.90 (m, 4H),7.66 (d, J=9.0 Hz, 2H), 4.64 (dd, J=8.4 Hz, 3.6 Hz, 1H), 4.61 (d, J=9.6Hz, 1H), 4.12 (dt, J=9.6 Hz, 6.6 Hz, 1H), 3.82 (dt, J=9.6 Hz, 6.6 Hz,1H), 2.38-2.31 (m, 2H), 2.25-2.19 (m, 2H), 2.14-2.02 (m, 2H), 1.82-1.77(m, 1H), 1.16 (d, J=6.6 Hz, 3H), 1.10 (d, J=7.2 Hz, 3H), 0.98 (d, J=6.6Hz, 3H), 0.94 (d, J=6.6 Hz, 3H) ppm;

¹³C NMR (151 MHz, MeOH-d₄): δ 179.2, 173.0, 169.1, 166.9, 141.3, 139.5,139.4, 135.9, 131.2, 130.3, 129.5, 128.9, 59.0, 57.9, 31.8, 31.1, 29.8,26.3, 21.4, 21.2, 19.5, 19.5 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₈H₃₅BClN₄O₇S [M−H₂O+H]⁺ 617.2003; found617.2002.

[α]D²⁰=−72.2 (c 0.36, MeOH).

Compound 52

(4-(((2S)-1-((2S)-2-((1-borono-2-methylpropyl)carbamoyl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-yl)carbamoyl)benzoyl)glycine(52)

Boc deprotection: In a culture tube equipped with a stir bar, S62 (55mg, 0.11 mmol) was dissolved in CH₂Cl₂ (1 mL). TFA (1 mL) was added at0° C. and the resulting solution was allowed to stir at 0° C. for 2 h.The volatiles were removed in vacuo using a rotary evaporator (waterbath temperature <25° C.), and the residue was used in next step withoutpurification.

Esterification:

Benzoic acid S64 (37 mg, 0.13 mmol, 1.2 equiv.) and PyBOP (69 mg, 0.13mmol, 1.2 equiv.) were then added and the mixture was dissolved in DMF(2.0 mL). N-methyl morpholine (49 μL, 0.45 mmol, 4.0 equiv.) was addedand the reaction was allowed to stir at room temperature for 3 h. Themixture was then diluted with EtOAc, washed with brine, dried overanhydrous Na₂SO₄, concentrated in vacuo and purified by flash columnchromatography (silica gel, 10:1 CH₂Cl₂: MeOH) to give the pinacolboronate (63 mg, 86%) which was used in the next step without furtherpurification.

Global Deprotection:

In a culture tube equipped with a stir bar, the aforementioned pinacolboronic ester (32 mg) was dissolved in CH₂Cl₂ (1 mL). TFA (1 mL) wasadded at 0° C. and the resulting solution was allowed to stir at roomtemperature overnight. The volatiles were removed in vacuo using arotary evaporator (water bath temperature <25° C.), and the residue waspurified by preparative reverse-phase HPLC (20-80% CH₃CN/H₂O over 40min, both CH₃CN and H₂O containing 0.1% TFA) and lyophilized to afford52 (13.0 mg, 52% over 3 steps).

Physical state: white powder;

¹H NMR (600 MHz, Methanol-d₄): δ 7.96-7.90 (m, 4H), 4.66-4.59 (m, 2H),4.16-4.07 (m, 3H), 3.83 (dt, J=10.1, 6.8 Hz, 1H), 2.40-2.29 (m, 2H),2.26-2.16 (m, 2H), 2.14-2.02 (m, 2H), 1.82-1.72 (m, 1H), 1.17 (d, J=6.7Hz, 3H), 1.12 (d, J=6.7 Hz, 3H), 0.98 (d, J=6.6 Hz, 3H), 0.95 (d, J=6.6Hz, 3H) ppm;

¹³C NMR (151 MHz, Methanol-d₄): δ 179.3, 173.1, 173.0, 169.50, 169.48,138.1, 138.0, 128.8, 128.6, 59.0, 58.0, 42.3, 31.8, 31.1, 29.8, 26.3,21.4, 21.2, 19.6, 19.5 ppm;

HRMS (ESI-TOF, m/z): Calcd for C₂₄H₃₄BN₄O₇[M−H₂O+H]⁺ 501.2515; found501.2516; [α]D²⁰=−97.3 (c 0.26, MeOH).

Stereochemistry Assignment of the Peptidic Boronic Acids 50, 51 and 52

The pinacol α-amino boronate S66a/S66b was prepared using the literatureprocedure (67) with slight modifications.

Compound S66a

(R)-2-methyl-N—((R)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl)propane-2-sulfinamide(S66a)

A culture tube equipped with a stirrer bar was charged sequentially withPCy₃.HBF₄ (12 mg, 0.033 mmol, 1.2 mol %), toluene (0.55 mL), aqueousCuSO₄ (1.1 mL, 0.03 M, 1.2 mol %) and benzylamine (15.3 μL, 0.14 mmol, 5mol %). The mixture was stirred for 10 min at the room temperature whena solution of aldimine S65 (480 mg, 2.74 mmol, 1.0 equiv.) in toluene(5.0 mL) was added, followed by B₂pin₂ (1.39 g, 5.5 mmol, 2.0 equiv.).The mixture was stirred vigorously for 14 h, diluted with EtOAc andfiltered through a silica gel plug eluting with EtOAc. The filtrate wasconcentrated and purified by flash column chromatography (silica gel,1:3 EtOAc:hexanes) to give S66a (1.07 g, d.r.>20:1) that wascontaminated with impurities originating from B₂pin₂ which could beremoved in the next step.

Compound S66b

(R)-2-methyl-N—((S)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl)propane-2-sulfinamide(S66b)

To a culture tube equipped with a stirrer bar were added a solution ofP(OPh)₃ (0.33 mL, 0.1 M in toluene, 1.2 mol %), aqueous CuSO₄ (1.1 mL,0.03 M, 1.2 mol %), and benzylamine (15.3 μL, 0.14 mmol, 5 mol %)sequentially. The mixture was stirred for 10 min, after which a solutionof aldimine S65 (480 mg, 2.74 mmol, 1.0 equiv.) in toluene (5.0 mL) andB₂pin₂ (1.39 g, 5.5 mmol, 2.0 equiv.) were added sequentially. Themixture was stirred vigorously for 14 h, diluted with EtOAc, andfiltered through a silica gel plug eluting with EtOAc. The filtrate wasconcentrated in vacuo, and purified by flash column chromatography(silica gel, 1:3 EtOAc:hexanes) to give S66b (857 mg, d.r.=6.1:1)contaminated with impurities originating from B₂pin₂ which could beremoved in the next step.

The α-boronic amine hydrochloride S67a/S67b was prepared using theliterature procedure (19)

Compound S67a

(R)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propan-1-aminehydrochloride (S67a)

S66a (190 mg, contaminated with B₂pin₂ impurities) was dissolved in1,4-dioxane (1.2 mL) and methanol (0.1 mL) under argon. HCl (80 μL, 4.0M in 1,4-dioxane) was added at room temperature and the resultingmixture was stirred at the same temperature before the volatiles wereremoved in vacuo. The resulting solid was triturated with a 2:1 mixtureof hexanes and Et₂O to give S67a (48 mg, 42% over 2 steps).

Physical state: white solid;

¹H NMR (600 MHz, CDCl₃) δ 8.23 (s, 3H), 2.79 (br s, 1H), 2.26 (pd,J=6.9, 4.8 Hz, 1H), 1.28 (br s, 12H), 1.11 (d, J=7.0 Hz, 3H), 1.10 (d,J=7.0 Hz, 3H).

¹³C NMR (151 MHz, CDCl₃) δ 85.2, 44.4 (br), 29.3, 25.2, 24.8, 20.4,19.9.

HRMS (ESI-TOF, m/z): Calcd for C₁₀H₂₃BNO₂ [M+H]⁺ 200.1816; found200.1812.

[α]D²⁰=−3.0 (C 1.0, CHCl₃).

Compound S67b

(S)-2-methyl-1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propan-1-aminehydrochloride (S67b)

S66b (350 mg, contaminated with Bpin impurities) was dissolved in1,4-dioxane (2.4 mL) and methanol (0.2 mL) under argon. HCl (0.16 mL,4.0 M in 1,4-dioxane) was added at room temperature and the resultingmixture was stirred at the same temperature before the volatiles wereremoved in vacuo. The resulting solid was triturated with a 2:1 mixtureof hexanes and Et₂O to give S67b (94 mg, 37% over 2 steps).

Physical state: white solid;

¹H NMR (600 MHz, CDCl₃) δ 8.25 (s, 3H), 2.80 (q, J=5.6 Hz, 1H), 2.26(pd, J=6.9, 4.9 Hz, 1H), 1.28 (br s, 12H), 1.12 (d, J=7.2 Hz, 3H), 1.11(d, J=7.2 Hz, 3H);

¹³C NMR (151 MHz, CDCl₃) δ 85.2, 44.5 (br), 29.3, 25.2, 24.8, 20.4,19.9;

HRMS (ESI-TOF, m/z): Calcd for C₁₀H₂₃BNO₂ [M+H]⁺ 200.1816; found200.1817;

[α]D²⁰=+2.7 (c 1.0, CHCl₃).

Compound S62a

To a culture tube charged with Boc-L-Val-L-Pro-OH (S68, 34 mg, 0.11mmol, 1.2 equiv.) and1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxid hexafluorophosphate (HATU, 44 mg, 0.12 mmol, 1.3 equiv.) wasadded DMF (0.5 mL), followed by diisopropylethylamine (45 μL, 0.26 mmol,2.9 equiv.). S67a (21 mg, 0.089 mmol) in DMF (1.0 mL) was added dropwiseat 0° C. After the completion of addition, the reaction was keptstirring at room temperature for 1 h. The mixture was diluted with Et₂O,washed with brine, dried over anhydrous Na₂SO₄, concentrated in vacuo.The resulting residue was purified by flash column chromatography(silica gel, 1:1 EtOAc:hexanes to 3:1 EtOAc:hexanes) to give S62a (32.3mg, 73%) as a colorless oil.

The NMR spectra of S62a are in agreements with those of S62 prepared viadecarboxylative borylation. This confirms the configuration of thestereocenter a to boron in S62 to be R.

Compound S62b

To a culture tube charged with Boc-L-Val-L-Pro-OH (S68, 26 mg, 0.083mmol, 1.2 equiv.) and1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxid hexafluorophosphate (HATU, 34 mg, 0.089 mmol, 1.3 equiv.) wasadded DMF (0.5 mL), followed by diisopropylethylamine (35 μL, 0.2 mmol,2.9 equiv.). S67b (16 mg, 0.068 mmol, 1.0 equiv.) in DMF (1.0 mL) wasadded dropwise at 0° C. After the completion of addition, the reactionwas kept stirring at room temperature for 1 h. The mixture was dilutedwith Et₂O, washed with brine, dried over anhydrous Na₂SO₄, concentratedin vacuo, and purified by flash column chromatography (silica gel, 1:1EtOAc:hexanes to EtOAc) to give S62b (22 mg, 65%) as a colorless oil.

Physical state: colorless oil;

R_(f)=0.60 (silica gel, 1:2 EtOAc:hexanes);

¹H NMR (600 MHz, CDCl₃) δ 7.08 (br s, 1H), 5.21 (d, J=9.3 Hz, 1H), 4.65(dd, J=8.2 Hz, 2.3 Hz, 1H), 4.28 (dd, J=9.4 Hz, 6.1 Hz, 1H), 3.70 (td,J=9.4 Hz, 7.1 Hz, 1H), 3.56 (ddd, J=9.6 Hz, 8.1 Hz, 3.4 Hz, 1H), 2.94(td, J=5.7 Hz, 2.6 Hz, 1H), 2.39 (ddd, J=12.8 Hz, 6.1 Hz, 2.6 Hz, 1H),2.14-2.05 (m, 1H), 1.98 (dtd, J=12.3 Hz, 6.8 Hz, 3.5 Hz, 2H), 1.88 (tdd,J=11.3 Hz, 9.0 Hz, 5.8 Hz, 2H), 1.42 (s, 9H), 1.21 (d, J=6.3 Hz, 12H),1.00 (d, J=6.8 Hz, 3H), 0.94 (d, J=6.8 Hz, 3H), 0.91 (d, J=6.8 Hz, 6H)ppm;

¹³C NMR (151 MHz, CDCl₃) δ 172.9, 171.8, 156.0, 83.1, 79.8, 59.0, 56.9,47.7, 45.5, 31.6, 29.8, 28.5, 27.2, 25.2, 25.12, 25.10, 20.4, 20.3,19.9, 17.7 ppm.

The NMR spectra of S62b differ from those of S62.

Elastase Inhibition Assay Compounds Tested:

For chemical structures, see FIG. 4A. For pharmokinetic profiles, seeFIG. 4B.

Materials and Methods:

Compounds 50-58, 50a, 50b, and 51a were subjected to this assay.

Serially diluted compounds in DMSO were dispensed into a 384-well blackopaque plate by Echo dispenser. 0.1 μg/mL human neutrophil elastase(EPC, Catalog # SE563, Owensville, Miss.) or human sputum diluted withassay buffer (100 mM HEPES, 500 mM NaCl, 0.02% Tween 20) was added intothe 384-well plate, and was incubated with different compounds atdifferent concentrations for 30 minutes at room temperature. The finalconcentration of DMSO in the reaction was 0.1%. Elastase substrateMeOSuc-AAPV-AMC (Bachem, Catalog #1-1270, Torrance, Calif.) of 100 μMfinal concentration was then added into the reaction system just beforeenzyme kinetics were read on PheraSTAR plate reader at excitation of 380nm and emission of 460 nm with a 3-minutes interval for 30 minutes intotal. Slope of fluorescence intensity vs. time representing the V_(max)of enzyme activity was calculated with MARS software. % relativeinhibition was calculated as:

$\frac{{Slope}_{DMSO} = {Slope}_{inhibitor}}{{Slope}_{DMSO}} \times 100\%$

IC₅₀ was calculated based on the % relative inhibition curve usinglog(agonist) vs. response (three parameters) method with Prism software.All experiments were performed in triplicate for at least threeindependent times. The IC₅₀ results of all experiments are shown as theaverage of triplicates with error bar indicating standard deviation asindicated in individual figures. For compounds 51, 52, and 58, the assayabove was repeated with 2.5, 25, 50 and 100 μM of elastase substrate(MeOSuc-AAPV-AMC) and Ki/nM values were calculated based on theseresults using the mixed model (68).

Quantification of Elastase Concentration in Human Sputum:

Human sputum was purchased from Discovery Life Sciences (Los Osos,Calif.). Human sputum was diluted 1:10 in volume with assay buffer (100mM HEPES, 500 mM NaCl, 0.02% Tween 20) followed by vigorous vortexing.The 1:10 diluted human sputum was further diluted into 1:30, 1:90,1:270, 1:810, and 1:2430. The elastase concentration was determined byelastase inhibition assay as described above. Specifically, a series ofstandards of human neutrophil elastase (starting at 2 μg/mL and furtherdiluted 1:2 in volume) were prepared in the assay buffer. The samplesand standards were plated in a 384-well black solid bottom plate; thesubstrate MeOSuc-AAPV-AMC of 100 μM final concentration was then addedinto the reaction system just before enzyme kinetics were read onPheraSTAR plate reader as mentioned above. The slope of enzymatickinetic reading was calculated by MARS software. The elastase levels ofthe human sputum were calculated based on the standard curve.

Results:

Purified NHE CF sputum COPD sputum Compound IC₅₀/nM LipE IC₅₀/nM LipEIC₅₀/nM LipE 50-B(OH)₂ 0.27 ± 0.02 8.37 0.51 ± 0.04 8.09 0.274 ± 0.0048.36 50a-C(O)CF₃ 134.9 ± 12.2  4.57 358.3 ± 54.5  4.15 178.9 ± 15.0 4.45 50b-CO₂H Not Active N.A. N.A. N.A  N.A. N.A. 51-B(OH)₂ 0.030 ±0.002 7.33 0.096 ± 0.002 6.83 0.0223 ± 0.0006 7.46 51a-C(O)CF₃ 289.8 ±32.1  1.95 833.4 ± 220.5 1.49 282.2 ± 23.1  1.96 52-B(OH)₂ 0.015 ± 0.00110.1 0.043 ± 0.002 9.62 0.0127 ± 0.0008 10.2 53 2.62 ± 0.39 7.32 4.08 ±0.39 7.11 2.98 ± 0.82 7.22 54 0.031 ± 0.002 6.76 0.40 ± 0.04 5.87 0.024± 0.003 6.85 55 0.093 ± 0.008 18.6 0.48 ± 0.03 17.8  0.051 ± 0.004 18.856 1.34 ± 0.13 4.59 2.68 ± 0.04 4.29 1.12 ± 0.04 4.67 57 0.99 ± 0.139.46 2.04 ± 0.08 9.16 0.97 ± 0.14 9.45 58 0.0111 ± 0.0002 5.04 202.8 ±31.2  0.77 16.23 ± 2.13  1.87 Note: Average ± SD, n = 3 plotted,representative of 3 independent, triplicate experiments. A non-linear,3-parameter log inhibitor curve was used to calculate the IC₅₀ values.Curve fit statistics: purified HNE, R² ≥ 0.95, CF patient sputum, R² ≥0.93, COPD patient sputum, R² ≥ 0.93.

Ki Values:

Compound 51 52 58 Ki/nM 0.034 0.0037 0.0027 Standard 0.002 0.0005 0.0029deviation Note: Measurements were performed in 3 replicates and averagevalues were reported.

Time Dependence of Elastase Inhibition Method:

The procedure for the elastase inhibition assay was followed with slightmodifications. 0.1 μg/mL human neutrophil elastase was incubated with arange of concentrations of inhibitors for 5, 15, 30 and 60 minutesbefore substrate MeOSuc-AAPV-AMC of 100 μM final concentration wasadded. Enzyme kinetics were read on PheraSTAR plate reader and IC₅₀ wascalculated with the method described above.

Results:

51 52 58 Standard Standard Standard Compound IC₅₀/nM deviation IC₅₀/nMdeviation IC₅₀/nM deviation 5 min 0.027 0.002 0.0040 0.0015 0.011 0.00215 min 0.030 0.007 0.0047 0.0009 0.0040 0.0011 30 min 0.037 0.005 0.00420.0015 0.0026 0.0003 60 min 0.026 0.010 0.0042 0.00076 0.00029 0.00021Note: Measurements were performed in 3 replicates and average valueswere reported.

Plasma Stability Assay Materials:

-   -   1) Compounds 50, 50a, 51, 51a and 52 were tested. Propantheline        was used as the reference compound in this assay; all stock        solutions were stored at −40° C. before use.    -   2) Test system: CD-1 Mouse Plasma from a minimum of 20 male        individuals were obtained from BioreclamationIVT (Catalog #:        MSEPLEDTA2-M; Batch #: MSE244515). EDTA-K2 was used as the        anticoagulant.

Procedure:

The frozen plasma was thawed in a water bath at 37° C. prior to theexperiments. The plasma was centrifuged at 4000 rpm for 5 min and theclots were removed if necessary. The pH was adjusted to 7.4±0.1 asnecessary. An intermediate solution (1 mM) was prepared and a 100 μMdosing solution was prepared by diluting 10 μL of the intermediatesolution with 90 μL 45% MeOH/H₂O. Duplicate of test samples were made bymixing 98 μL of blank plasma with 2 μL of dosing solution (100 μM) toachieve the final concentration of 2 μM. Samples were incubated at 37°C. At each time point (0, 10, 30, 60, and 120 min), 400 μL of stopsolution (consisting of 200 ng/mL tolbutamide and 20 ng/mL buspirone in50% MeOH/CH₃CN) was added to precipitate protein under thorough mixing.The sample plates were then centrifuged at 4,000 rpm for 10 min. Analiquot of supernatant (100 μL) was transferred from each well and mixedwith 200 of μL ultrapure water. The samples were shaken at 800 rpm forabout 10 min before LC-MS/MS analysis.

Data Analysis:

The % remaining of test compound after incubation in plasma wascalculated using following equation:

% Remaining=100×(P _(AR) at T _(n) /P _(AR) at T ₀)

where P_(AR) is the peak area ratio of analyte versus internal standard(IS) and The appointed incubation time points are T₀ (0 min), T_(n)(n=0, 10, 30, 60, 120 min).

LC-MS/MS Condition:

Each compound was analyzed by LC/MS using an ACE 5-phenyl 50×2.1 mmcolumn (Part No. ACE-125-0502) with 0.1% formic acid in water and 0.1%formic acid in acetonitrile as the mobile phases. Tobultamide was usedas the internal standard. Data collected were processed by Analyst 1.6.2software and MultiQuant 3.0.2 software.

Results:

Time Point % Compound Species/Matrix (min) Remaining (mean) 50 CD-1Mouse Plasma 0 100.0 10 100.5 30 105.2 60 88.0 120 76.7 50a CD-1 MousePlasma 0 100.0 10 101.7 30 98.8 60 100.0 120 92.5 51 CD-1 Mouse Plasma 0100.0 10 90.0 30 79.4 60 84.1 120 90.3 51a CD-1 Mouse Plasma 0 100.0 1099.0 30 109.1 60 99.5 120 106.6 52 CD-1 Mouse Plasma 0 100.0 10 116.1 30104.8 60 96.4 120 79.2 Propantheline CD-1 Mouse Plasma 0 100.0 10 76.830 39.1 60 21.7 120 7.7

Mouse Liver Microsomal Metabolic Stability Assay Materials:

1) Compounds 50, 50a, 51, 51a, and 52 were tested in this assay.Testosterone, Dichlofenac, and Propafenone were used as control.

2) Buffers:

1. 100 mM potassium phosphate buffer, pH 7.4.

2. 10 mM MgCl₂

3) Compound Dilution:

Intermediate solution was prepared by diluting 5 μL of compound orcontrol stock solution (10 mM in DMSO) with DMSO (45 μL) and 1:1Methanol/Water (450 μL) (concentration=100 μM, 45% MeOH). Workingsolution was prepared by diluting 50 μL of the intermediate solutionwith 450 μL of 100 mM potassium phosphate buffer, pH=7.4 (centration=10μM, 4.5% MeOH).

4) NADPH regenerating system (final Isocitric dehydrogenaseconcentration=1 unit/mL at incubation) comprised:β-Nicotinamide adenine dinucleotide phosphate acquired from Sigma(Catalog # N0505), isocitric acid from Sigma (Cat. No. 11252) andisocitric dehydrogenase from Sigma (Catalog #12002).5) Liver microsome solution (final concentration of 0.5 mg protein/mL)was prepared using Mouse liver microsomes from Xenotech (Catalog #M1000, Lot #1310028).6) Stop solution: Cold acetonitrile containing 100 ng/mL Tolbutamide and100 ng/mL Labetalol as internal standards (IS)

Procedure:

10 μL/well of compound working solution or control working solution wasadded to all plates (T0, T5, T10, T20, T30, T60, NCF60) except thematrix blank. 80 μL/well of microsome solution was added to every plate.The mixtures of microsome solution and compound were incubated at 37° C.for about 10 min. 10 μL/well of NADPH regenerating system (pre-warmed to37° C.) was then added to every plate to start the reaction. The plateswere incubated for the durations indicated (matrix blank: 1 h; T60: 1 h;T30: 31 min; T20: 40 min; T10 50 min; T5: 55 min). For NCF60(abbreviation of no co-factor) no NADPH regenerating system was added,but was replaced by 10 μL/well of potassium phosphate buffer (100 mM, pH7.4); the resulting mixture was incubated at 37° C. for 1 h.

The reactions were then terminated with the stop solution (cold at 4°C.) containing 100 ng/mL Tolbutamide and 100 ng/mL Labetalol (300μL/well). The sampling plates were shaken for approximately 10 minutes,then were centrifuged at 4000 rpm for 20 min at 4° C. Whilecentrifuging, 8 new 96 well plates were loaded with 300 μL of HPLC gradewater. 100 μL of supernatant was finally added to 300 μL of HPLC gradewater and mixed for LC/MS/MS analysis.

Apricot pipetting robot was used for all additions, mixing, andtransformations described above in 96-well plate format.

Data Analysis

The equation of first order kinetics was used to calculate T_(1/2) andCl_(int(mic)):

  C_(t) = C_(o) ⋅ e^(−k_(e) ⋅ t)${{{{when}\mspace{14mu} C_{t}} = {\frac{1}{2}C_{o}}},{T_{1/2} = {\frac{\ln \; 2}{k_{e}} = {0.693/k_{e}}}}}\mspace{20mu}$${CL}_{{int}{({mic})}} = {\frac{0.693}{{in}\mspace{14mu} {vitro}\mspace{14mu} T_{1/2}} \cdot \left( \frac{1}{\frac{mg}{mL}{microsomal}\mspace{14mu} {protein}\mspace{14mu} {in}\mspace{14mu} {reaction}\mspace{14mu} {system}} \right)}$${CL}_{{int}{({liver})}} = {{CL}_{{int}{({mic})}} \cdot \left( \frac{{mg}\mspace{14mu} {microsomes}}{g\mspace{14mu} {liver}} \right) \cdot \left( \frac{g\mspace{14mu} {liver}}{{Kg}\mspace{14mu} {body}\mspace{14mu} {weight}} \right)}$

Results:

MLM 0.5 CL_(int(mic)) CL_(int(liver)) Extraction Remaining RemainingCompounds R² T_(1/2)(min) (μL/min/mg) (mL/min/kg) ratio (T = 60 min)(*NCF = 60 min) 50 0.8919 >145 <9.6 <38.0 <0.3 78.5% 99.0% 50a0.6722 >145 <9.6 <38.0 <0.3 92.9% 82.3% 51 0.2713 >145 <9.6 <38.0 <0.385.8% 95.0% 51a 0.9190 71.6 19.4 76.6 0.5 52.2% 91.7% 52 0.4436 >145<9.6 <38.0 <0.3 78.9% 103.6%  Testosterone 0.9992 2.3 597.4 2365.5 1.00.0% 70.3% Diclofenac 0.9820 51.0 27.2 107.6 0.5 43.0% 88.0% Propafenone0.9858 1.3 1.3 4188.4 1.0 0.2% 84.3% Notes: 1)* NCF: the abbreviation ofno co-factor. No NADPH regenerating system was added into NCF samples(replaced by buffer) during the 60 min-incubation, if the NCF remainingis less than 60%, then Non-NADPH dependent occurs. 1) R² is thecorrelation coefficient of the linear regression for the determinationof kinetic constant. 2) T_(1/2) is half-life and CL_(int(rnic)) is theintrinsic clearance.${\left. 3 \right)\mspace{14mu} \frac{{mg}\mspace{14mu} {microsomes}}{g\mspace{14mu} {liver}}} = {45\mspace{14mu} {mg}\text{/}g\mspace{14mu} {for}\mspace{20mu} {five}{\mspace{11mu} \;}{{species}.}}$${\left. 4 \right)\mspace{14mu} \frac{g\mspace{14mu} {liver}\mspace{14mu} {weight}}{{Kg}\mspace{14mu} {body}\mspace{14mu} {weight}}} = {88\mspace{14mu} g\text{/}{Kg}\mspace{14mu} {for}\mspace{20mu} {{mouse}.}}$${\left. 5 \right)\mspace{14mu} {Hepatic}\mspace{14mu} {blood}\mspace{14mu} {clearance}\mspace{14mu} ({CLH})} = \frac{{{Clint}({liver})} \times {Qh}}{{{Clint}({liver})} + {Qh}}$${{Hepatic}\mspace{14mu} {extraction}\mspace{14mu} {ratio}\mspace{14mu} ({EH})} = {\frac{CLH}{QH} = \frac{{Clint}({liver})}{{{Clint}({liver})} + {Qh}}}$Whereby Qh(mL/min/Kg liver) = 90.0 mL/min/Kg for mouse liver

Kinetic Solubility Test Materials:

Compounds 50, 50a, 51, 51a, and 52 were tested.

Procedure:

The stock solution of each compound (10 μL; 10 mM in DMSO) was dilutedwith phosphate buffer solution (490 μL; 50 mM, pH 6.8). The resultingmixture was shaken for 24 h. Samples were then filtered. Kineticsolubility was then determined by UV spectroscopy [calibrated by astandard curve (1, 20, and 200 μM)].

Results:

Kinetic Solubility pH = 6.8 Kinetic Solubility pH = 6.8 Compound (μg/mL)(μM) 50 >74.25 >200.00 50a >84.69 >200.00 51 >126.99 >200.00 51a 119.75174.28 52 >103.67 >200.00

Caco-2 Permeability Assay Materials:

-   -   1) Caco-2 culture: Caco-2 cells purchased from ATCC were seeded        onto polyethylene membranes (PET) in 96-well BD Insert plates at        1×105 cells/cm2, and refreshed medium every 4-5 days until to        the 21st to 28th day for confluent cell monolayer formation.    -   2) Compound information: compounds 51 and 51a were subjected to        the assay. Digoxin, fenoterol, and propranol were used as        standards respectively.

Transport Method:

The transport buffer used in the study was HBSS with 10 mM HEPES at pH7.40±0.05. Compounds were tested at 2 μM bi-directionally in duplicates.Digoxin was tested at 10 μM bi-directionally in a duplicate, whilefenoterol and propranolol were tested at 2 μM in A (apical) to B(basolateral) direction in duplicates. The final DMSO concentration wasadjusted to less than 1%. The plate was incubated for 2 hours in a CO₂incubator at 37±1° C., with 5% CO₂ at saturated humidity withoutshaking. All samples, after mixing with acetonitrile containing internalstandard, were centrifuged at 4000 rpm for 20 min. Subsequently, 100 μLsupernatant solution was diluted with 100 μL distilled water forLC/MS/MS analysis. Concentrations of test and control compounds instarting solution, donor solution, and receiver solution were quantifiedby LC/MS/MS methodologies, using peak area ratio of analyte/internalstandard. After transport assay, lucifer yellow rejection assay wasapplied to determine the Caco-2 cell monolayer integrity. All datapresented herein have passed this test.

Data Analysis:

The apparent permeability coefficient Papp (cm/s) was calculated usingthe equation:

$P_{app} = {\left( \frac{{dC}_{r}}{dt} \right) \cdot {V_{r}/\left( {A \cdot C_{0}} \right)}}$

Where

$\frac{{dC}_{r}}{dt}$

is the cumulative concentration of compound in the receiver chamber as afunction of time (μM/s); V_(r) is the solution volume in the receiverchamber (0.075 mL on the apical side, 0.25 mL on the basolateral side);A is the surface area for the transport, i.e. 0.0804 cm² for the area ofthe monolayer; Co is the initial concentration in the donor chamber(μM).The efflux ratio was calculated using the equation:

Efflux ratio=P _(app)(BA)/P _(app)(AB)

Percent recovery was calculated using the equation:

% Recovery=100×[(V _(r) ·C _(r))+(V _(d) ·C _(d))]/(V _(d) ·C ₀)

Where V_(d) is the volume in the donor chambers (0.075 mL on the apicalside, 0.25 mL on the basolateral side); C_(d) and C_(r) are the finalconcentrations of transport compound in donor and receiver chambers,respectively.

LC/MS Conditions:

Each compound was analyzed by LC/MS using an ACE 5-phenyl 50×2.1 mmcolumn (Part No. ACE-125-0502) with 0.1% formic acid in water and 0.1%formic acid in acetonitrile as the mobile phases. Tobultamide was usedas the internal standard. Data collected were processed by Analyst 1.6.2software and MultiQuant 3.0.2 software.

Results:

Mean P_(app) (10⁻⁶ cm/s) Efflux Mean Recovery % Compound ID A to B B toA Ratio A to B B to A Fenoterol 0.24 ND — 93.38 ND Propranolol 19.76 ND— 69.25 ND Digoxin <0.02 8.50 >364.02 <91.21 100.33 51 <0.16 0.61 >3.91<88.25 99.12 51a <0.08 <0.12 NA <74.15 <90.87 Note: 1) For digoxin andtest compound, the signal responses in receiver samples were lower thanthe limit of quantification. For the convenience of calculating P_(app)values, 50 was used as the peak area of analyte in receiver samplesinstead. 2) The permeation was assessed over a 120-minute incubation at37 ± 1° C. and 5% CO₂ with saturated humidity.

Summary of ADME Data for Boronates 51 and 52 Compared toTrifluoromethylketone 51a

CD-1 Mouse Microsomal Plasma % stability Kinetic solubility Remaining(Mouse Caco-2 (P_(app) A-B) Caco-2 (P_(app) B-A) Compound (pH 6.8) [μM]@ 2 hr [%] ER) [10⁻⁶ cm/s] [10⁻⁶ cm/s] 51 - B(OH)₂ >200 90.3% <0.3<0.080 <0.12 51a - C(O)CF₃ 174.28 106.6% <0.3 <0.16 0.61 52 -B(OH)₂ >200 79.2% <0.3

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All patents and publications referred to herein are incorporated byreference herein to the same extent as if each individual publicationwas specifically and individually indicated to be incorporated byreference in its entirety.

What is claimed is:
 1. A method of converting an alkyl carboxylic acidcompound RCO₂H to a corresponding alkyl boronic pinacolato estercompound

wherein R is a hydrocarbyl group comprising an sp³ hybridized carbonatom bonded to the CO₂H or the boron atom, respectively, R optionallyfurther comprising alkyl or alkenyl groups, both optionally comprisingheteroatoms, or optionally comprising aryl, heterocyclyl, or heteroarylgroups, or any combination thereof; the method comprising: a) forming aredox active ester (RAE) of the alkyl carboxylic acid compound; then, b)contacting the redox active ester of the alkyl carboxylic acid compoundin an aprotic solvent, and bis(pinacolato)diboron (B₂pin₂), in thepresence of at least 20 mole % of a Mg(II) salt and of at least onemolar equivalent a lithium compound comprising a (C1-C4)alkyllithium, a(C1-C4)alkoxylithium, or lithium hydroxide, and at least 10 mole % of aCu or Ni salt; in the presence of a 1,3-dicarbonyl ligand forming withthe Cu a compound of formula (M)

wherein R_(1A) and R_(2A) are each independently selected (C1-C4)alkyl,trifluoromethyl, or phenyl; or in the presence of a ligand of formula(L) comprising a bipyridyl of formula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl; to provide the corresponding alkyl boronic pincolato estercompound


2. The method of claim 1, comprising: a) forming a redox active ester(RAE) of the alkyl carboxylic acid compound; then, b) either: 1)contacting in aprotic solvent the redox active ester,bis(pinacolato)diboron (B₂pin₂), and effective amounts of a Mg(II) saltin the present of lithium hydroxide or a lithium (C1-C4)alkoxide, and inthe presence of a Cu(I) or a Cu(II) complex or both of a 1,3-dicarbonylcompound, the complex being of formula (M)

wherein R_(1A) and R_(2A) are each independently selected (C1-C4)alkyl,trifluoromethyl, or phenyl, or of a Cu(I) or a Cu(II) salt or both andan effective amount of a ligand (L) comprising a bipyridyl of formula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl; to provide the pinacolato ester of the corresponding alkylboronic ester compound; or: 2) contacting in aprotic solution the redoxactive ester and effective amounts of a Ni(II) salt and a Mg(II) salt,in the presence of an effective amount of a ligand (L) comprising abipyridyl of formula

wherein R₁ and R₂ are each independently selected (C1-C4)alkyl or(C1-C4)alkoxy, n1 and n2 are each independently 0, 1, or 2, or of a1,10-phenanthroline of formula

wherein R₃ and R₄ are each independently (C1-C4)alkyl, (C1-C4)alkoxy orphenyl; then, adding a premixed solution comprising an organolithiumcompound and at least one molar equivalent bis(pinacolato)diboron(B₂pin₂); to provide the pinacolato ester of the corresponding alkylboronic ester compound.
 3. The method of claim 1 or 2 wherein the redoxactive ester of the alkyl carboxylic acid is an N-hydroxyphthalimide ora tetrachloro-N-hydroxyphthalimide ester.
 4. The method of claim 1 or 2wherein the Cu(II) complex of a 1,3-dicarbonyl compound, of formula (M),is Cu(acac)₂ (M1).
 5. The method of claim 1 or 2 wherein the Ni(II) saltis NiCl₂.
 6. The method of claim 1 or 2 wherein the Mg(II) salt is MgBr₂or MgCl₂.
 7. The method of claim 1 or 2 wherein for a Ni catalyst theorganolithium compound is methyllithium or wherein for a Cu catalyst thelithium compound is LiOH or a lithium (C1-C4)alkoxide.
 8. The method ofclaim 1 or 2 wherein the aprotic solvent comprises THF or dioxane, andDMF.
 9. The method of claim 1 or 2 further comprising step c) cleavingunder acidic conditions the pinacolato ester of the alkyl boronic acidcompound

to provide the alkyl boronic acid compound RB(OH)₂.
 10. The method ofclaim 9 wherein the step of cleaving the pinacolato ester of the alkylbornic acid compound comprises contacting the ester with BCl₃ followedwith methanol, or contacting the ester with trifluoroacetic acid, orcontacting the ester with a boronic acid in aqueous HCl.
 11. The methodof claim 10 wherein the boronic acid is phenylboronic acid or2-methylpropylboronic acid.
 12. The method of claim 1 or 2 wherein theligand (L) is of formula L1-L5

wherein R1=OMe, R2=H, L1 R1=tBu, R2=H, L2 R1=H, R2=H, L3 R1=Me, R2=H, L4R1=OMe, R2=OMe, L5; or wherein the ligand (L) is of formula L7-L9

wherein R3=H, R4=H, L7 R3=Ph, R4=H, L8 R3=OMe, R4=H, L9.
 13. The methodof preparation of alkyl boronic compound ninlaro

from alkyl carboxylic acid compound

by carrying out the steps a), b), and c) of claim 9, starting with thealkyl carboxylic acid compound.
 14. The method of preparing a boronateester analog of atorvastatin ketal, comprising, first, a) forming theNHPI ester of atorvastatin ketal to provide the redox active ester

then, carrying out step b) of claim 1 or 2, on the redox activatedester, to provide the boronate ester of an analog of atorvastatin ketal


15. A boronate ester analog of atorvastatin ketal of formula


16. A boronic acid analog of atorvastatin ketal of formula


17. The method of preparing a dimethyl-t-butylsilyl (TBS)hydroxyl-protected boronic acid analog of a vancomycin aglycone

comprising, first, a) converting carboxylic acid

to the corresponding NHPI redox activated ester; then, carrying out stepb) of claim 2 on the redox activated ester to provide an O-protectedboronate pinacolato ester of the boronic acid, then, cleaving theboronic ester group by contacting the ester with BCl₃ followed withmethanol, or by contacting the ester with trifluoroacetic acid, or bycontacting the ester with a boronic acid in aqueous HCl, to provide theO-protected boronic acid compound of formula


18. A hydroxyl-protected boronic acid analog of vancomycin aglycone

wherein TBS signifies a dimethyl-t-butylsilyl 0-protecting group.
 19. AnOH-deprotected boronic acid analog of vancomycin aglycone of formula


20. The method of preparing boronic acid mCBK319 elastase inhibitorcompound

comprising carrying out steps a), b), and c) of claim 9, starting withcompound


21. A boronic acid mCBK319 elastase inhibitor compound of formula


22. The method of preparing boronic pinacolato ester compound of formula

comprising carrying out step b), of claim 1 or 2, starting with compound

to provide the Boc-protected boronic pinacolato ester compound


23. The method of claim 22, further comprising cleaving the Boc group ofthe Boc-protected boronic pinacolato ester compound with trifluoroaceticacid, followed by condensation of the resulting free amino group withcompound of formula

followed by cleavage of pinacolato boronate ester group withphenylboronic acid in aqueous HCl to provide the boronic acid mCBK320elastase inhibitor compound of formula


24. A boronic acid mCBK320 elastase inhibitor compound of formula


25. The method of claim 22, further comprising cleaving the Boc groupand the boronate ester of the Boc-protected boronic pinacolato estercompound with trifluoroacetic acid, followed by condensation of theresulting free amino group with a compound of formula

followed by cleavage of the t-Bu ester, to provide a boronic acidmCBK323 elastase inhibitor compound of formula)


26. A boronic acid mCBK323 elastase inhibitor compound of formula


27. The method of preparation of an arylomycin sidechain analog boronicacid

comprising carrying out the conversions of claim 9, followed by removalof the N-Boc groups with acid, starting with an arylomycin sidechainanalog carboxylic acid of formula


28. An arylomycin sidechain analog boronic acid of formula


29. The method of preparation of claim 1 or 2 of a compound of formula

wherein TBDMS signifies a t-butyldimethylsilyl protecting group,comprising first, a) forming a redox active ester of a carboxylic acidof formula

then carrying out step b) of claim 1 or 2 to provide the compound offormula


30. The method of synthesis of a cyclic boronic acid 1-LactamaseInhibitor (RPX7009) of formula

comprising the method of claim 29.